Groupthink

From Wikipedia, the free encyclopedia

Groupthink is a psychological phenomenon that occurs within a group of people in which the desire for harmony or conformity in the group results in an irrational or dysfunctional decision-making outcome. Group members try to minimize conflict and reach a consensus decision without critical evaluation of alternative viewpoints by actively suppressing dissenting viewpoints, and by isolating themselves from outside influences.

Groupthink requires individuals to avoid raising controversial issues or alternative solutions, and there is loss of individual creativity, uniqueness and independent thinking. The dysfunctional group dynamics of the "ingroup" produces an "illusion of invulnerability" (an inflated certainty that the right decision has been made). Thus the "ingroup" significantly overrates its own abilities in decision-making and significantly underrates the abilities of its opponents (the "outgroup"). Furthermore, groupthink can produce dehumanizing actions against the "outgroup".

Antecedent factors such as group cohesiveness, faulty group structure, and situational context (e.g., community panic) play into the likelihood of whether or not groupthink will impact the decision-making process.

Groupthink is a construct of social psychology but has an extensive reach and influences literature in the fields of communication studies, political science, management, and organizational theory,^[1] as well as important aspects of deviant religious cult behaviour.^[2][3]

Groupthink is sometimes stated to occur (more broadly) within natural groups within the community, for example to explain the lifelong different mindsets of conservatives versus liberals,^[4] or the solitary nature of introverts.^[5] However, this conformity of viewpoints within a group does not mainly involve deliberate group decision-making, and might be better explained by the collective confirmation bias of the individual members of the group.

Most of the initial research on groupthink was conducted by Irving Janis, a research psychologist from Yale University.^[6] Janis published an influential book in 1972, which was revised in 1982.^[7][8] Janis used the Bay of Pigs disaster (the failed invasion of Castro's Cuba in 1961) and the Japanese attack on Pearl Harbor in 1941 as his two prime case studies. Later studies have evaluated and reformulated his groupthink model.^[9][10]

History

From "Groupthink" by William H. Whyte, Jr. in Fortune magazine, March 1952

William H. Whyte, Jr. coined the term in 1952 in Fortune magazine:

Groupthink being a coinage – and, admittedly, a loaded one – a working definition is in order. We are not talking about mere instinctive conformity – it is, after all, a perennial failing of mankind. What we are talking about is a rationalized conformity – an open, articulate philosophy which holds that group values are not only expedient but right and good as well.^[11][12]

Irving Janis pioneered the initial research on the groupthink theory. He does not cite Whyte, but coined the term by analogy with "doublethink" and similar terms that were part of the newspeak vocabulary in the novel Nineteen Eighty-Four by George Orwell. He initially defined groupthink as follows:

I use the term groupthink as a quick and easy way to refer to the mode of thinking that persons engage in when concurrence-seeking becomes so dominant in a cohesive ingroup that it tends to override realistic appraisal of alternative courses of action. Groupthink is a term of the same order as the words in the newspeak vocabulary George Orwell used in his dismaying world of 1984. In that context, groupthink takes on an invidious connotation. Exactly such a connotation is intended, since the term refers to a deterioration in mental efficiency, reality testing and moral judgments as a result of group pressures.^[6]:43

He went on to write:

The main principle of groupthink, which I offer in the spirit of Parkinson's Law, is this: The more amiability and esprit de corps there is among the members of a policy-making ingroup, the greater the danger that independent critical thinking will be replaced by groupthink, which is likely to result in irrational and dehumanizing actions directed against outgroups.^[6]:44

Janis set the foundation for the study of groupthink starting with his research in the American Soldier Project where he studied the effect of extreme stress on group cohesiveness. After this study he remained interested in the ways in which people make decisions under external threats. This interest led Janis to study a number of "disasters" in American foreign policy, such as failure to anticipate the Japanese attack on Pearl Harbor (1941); the Bay of Pigs Invasion fiasco (1961); and the prosecution of the Vietnam War (1964–67) by President Lyndon Johnson. He concluded that in each of these cases, the decisions occurred largely because of groupthink, which prevented contradictory views from being expressed and subsequently evaluated.

After the publication of Janis' book Victims of Groupthink in 1972,^[7] and a revised edition with the title Groupthink: Psychological Studies of Policy Decisions and Fiascoes in 1982,^[8] the concept of groupthink was used^{[by whom?]} to explain many other faulty decisions in history. These events included Nazi Germany's decision to invade the Soviet Union in 1941, the Watergate Scandal and others. Despite the popularity of the concept of groupthink, fewer than two dozen studies addressed the phenomenon itself following the publication of Victims of Groupthink, between the years 1972 and 1998.^[1]:107 This is surprising considering how many fields of interests it spans, which include political science, communications, organizational studies, social psychology, management, strategy, counseling, and marketing. One can most likely explain this lack of follow-up in that group research is difficult to conduct, groupthink has many independent and dependent variables, and it is unclear "how to translate [groupthink's] theoretical concepts into observable and quantitative constructs."^{[1]:107–108}

Nevertheless, outside research psychology and sociology, wider culture has come to detect groupthink (somewhat fuzzily defined) in observable situations, for example:

• " [...] critics of Twitter point to the predominance of the hive mind in such social media, the kind of groupthink that submerges independent thinking in favor of conformity to the group, the collective"^[13]

• "[...] leaders often have beliefs which are very far from matching reality and which can become more extreme as they are encouraged by their followers. The predilection of many cult leaders for abstract, ambiguous, and therefore unchallengeable ideas can further reduce the likelihood of reality testing, while the intense milieu control exerted by cults over their members means that most of the reality available for testing is supplied by the group environment. This is seen in the phenomenon of 'groupthink', alleged to have occurred, notoriously, during the Bay of Pigs fiasco."^[14]

• "Groupthink by Compulsion [...] [G]roupthink at least implies voluntarism. When this fails, the organization is not above outright intimidation. [...] In [a nationwide telecommunications company], refusal by the new hires to cheer on command incurred consequences not unlike the indoctrination and brainwashing techniques associated with a Soviet-era gulag."^[15]

Symptoms

To make groupthink testable, Irving Janis devised eight symptoms indicative of groupthink.
Type I: Overestimations of the group — its power and morality

1. Illusions of invulnerability creating excessive optimism and encouraging risk taking.
2. Unquestioned belief in the morality of the group, causing members to ignore the consequences of their actions.

Type II: Closed-mindedness

1. Rationalizing warnings that might challenge the group's assumptions.
2. Stereotyping those who are opposed to the group as weak, evil, biased, spiteful, impotent, or stupid.

Type III: Pressures toward uniformity

1. Self-censorship of ideas that deviate from the apparent group consensus.
2. Illusions of unanimity among group members, silence is viewed as agreement.
3. Direct pressure to conform placed on any member who questions the group, couched in terms of "disloyalty"
4. Mindguards— self-appointed members who shield the group from dissenting information.

Causes

Janis prescribed three antecedent conditions to groupthink.^[7]:9

1. High group cohesiveness

Janis emphasized that cohesiveness is the main factor that leads to groupthink. Groups that lack cohesiveness can of course make bad decisions, but they do not experience groupthink. In a cohesive group, members avoid speaking out against decisions, avoid arguing with others, and work towards maintaining friendly relationships in the group. If cohesiveness gets to such a high level where there are no longer disagreements between members, then the group is ripe for groupthink.

• deindividuation: group cohesiveness becomes more important than individual freedom of expression

2. Structural faults

Cohesion is necessary for groupthink, but it becomes even more likely when the group is organized in ways that disrupt the communication of information, and when the group engages in carelessness while making decisions.

• insulation of the group: can promote the development of unique, inaccurate perspectives on issues the group is dealing with, and can then lead to faulty solutions to the problem.
• lack of impartial leadership: leaders can completely control the group discussion, by planning what will be discussed, only allowing certain questions to be asked, and asking for opinions of only certain people in the group. Closed style leadership is when leaders announce their opinions on the issue before the group discusses the issue together. Open style leadership is when leaders withheld their opinion until a later time in the discussion. Groups with a closed style leader have been found to be more biased in their judgments, especially when members had a high degree for certainty. Thus, it is best for leaders to take an open style leadership approach, so that the group can discuss the issue without any pressures from the leader.
• lack of norms requiring methodological procedures
• homogeneity of members' social backgrounds and ideology

3. Situational context:

• highly stressful external threats: High stake decisions can create tension and anxiety, and group members then may cope with the decisional stress in irrational ways. Group members may rationalize their decision by exaggerating the positive consequences and minimizing the possible negative consequences. In attempt to minimize the stressful situation, the group will make a quick decision with little to no discussion or disagreement about the decision. Studies have shown that groups under high stress are more likely to make errors, lose focus of the ultimate goal, and use procedures that members know have not been effective in the past.
• recent failures: can lead to low self-esteem, resulting in agreement with the group in fear of being seen as wrong.
• excessive difficulties on the decision-making task

time pressures: group members are more concerned with efficiency and quick results, instead of quality and accuracy. Additionally, time pressures can lead to group members overlooking important information regarding the issue of discussion.

• moral dilemmas

Although it is possible for a situation to contain all three of these factors, all three are not always present even when groupthink is occurring. Janis considered a high degree of cohesiveness to be the most important antecedent to producing groupthink and always present when groupthink was occurring; however, he believed high cohesiveness would not always produce groupthink. A very cohesive group abides to all group norms; whether or not groupthink arises is dependent on what the group norms are. If the group encourages individual dissent and alternative strategies to problem solving, it is likely that groupthink will be avoided even in a highly cohesive group. This means that high cohesion will lead to groupthink only if one or both of the other antecedents is present, situational context being slightly more likely than structural faults to produce groupthink.^[16]

Prevention

As observed by Aldag & Fuller (1993), the groupthink phenomenon seems to rest on a set of unstated and generally restrictive assumptions:^[17]

1. The purpose of group problem solving is mainly to improve decision quality
2. Group problem solving is considered a rational process.
3. Benefits of group problem solving:
   • variety of perspectives
   • more information about possible alternatives
   • better decision reliability
   • dampening of biases
   • social presence effects
4. Groupthink prevents these benefits due to structural faults and provocative situational context
5. Groupthink prevention methods will produce better decisions
6. An illusion of well-being is presumed to be inherently dysfunctional.
7. Group pressures towards consensus lead to concurrence-seeking tendencies.

It has been thought that groups with the strong ability to work together will be able to solve dilemmas in a quicker and more efficient fashion than an individual. Groups have a greater amount of resources which lead them to be able to store and retrieve information more readily and come up with more alternative solutions to a problem. There was a recognized downside to group problem solving in that it takes groups more time to come to a decision and requires that people make compromises with each other. However, it was not until the research of Janis appeared that anyone really considered that a highly cohesive group could impair the group's ability to generate quality decisions. Tight-knit groups may appear to make decisions better because they can come to a consensus quickly and at a low energy cost; however, over time this process of decision-making may decrease the members' ability to think critically. It is, therefore, considered by many to be important to combat the effects of groupthink.^[16]

According to Janis, decision-making groups are not necessarily destined to groupthink. He devised ways of preventing groupthink:^{[7]:209–215}

1. Leaders should assign each member the role of "critical evaluator". This allows each member to freely air objections and doubts.
2. Leaders should not express an opinion when assigning a task to a group.
3. Leaders should absent themselves from many of the group meetings to avoid excessively influencing the outcome.
4. The organization should set up several independent groups, working on the same problem.
5. All effective alternatives should be examined.
6. Each member should discuss the group's ideas with trusted people outside of the group.
7. The group should invite outside experts into meetings. Group members should be allowed to discuss with and question the outside experts.
8. At least one group member should be assigned the role of Devil's advocate. This should be a different person for each meeting.

By following these guidelines, groupthink can be avoided. After the Bay of Pigs invasion fiasco, President John F. Kennedy sought to avoid groupthink during the Cuban Missile Crisis using "vigilant appraisal."^{[8]:148–153} During meetings, he invited outside experts to share their viewpoints, and allowed group members to question them carefully. He also encouraged group members to discuss possible solutions with trusted members within their separate departments, and he even divided the group up into various sub-groups, to partially break the group cohesion. Kennedy was deliberately absent from the meetings, so as to avoid pressing his own opinion.

Empirical findings and meta-analysis

Testing groupthink in a laboratory is difficult because synthetic settings remove groups from real social situations, which ultimately changes the variables conducive or inhibitive to groupthink.^[18] Because of its subjective nature, researchers have struggled to measure groupthink as a complete phenomenon, instead frequently opting to measure its particular factors. These factors range from causal to effectual and focus on group and situational aspects.^[19][20]

Park (1990) found that "only 16 empirical studies have been published on groupthink," and concluded that they "resulted in only partial support of his [Janis's] hypotheses."^[21]:230 Park concludes, "despite Janis' claim that group cohesiveness is the major necessary antecedent factor, no research has showed a significant main effect of cohesiveness on groupthink."^[21]:230 Park also concludes that research on the interaction between group cohesiveness and leadership style does not support Janis' claim that cohesion and leadership style interact to produce groupthink symptoms.^[21] Park presents a summary of the results of the studies analyzed. According to Park, a study by Huseman and Drive (1979) indicates groupthink occurs in both small and large decision-making groups within businesses.^[21] This results partly from group isolation within the business. Manz and Sims (1982) conducted a study showing that autonomous work groups are susceptible to groupthink symptoms in the same manner as decisions making groups within businesses.^[21][22] Fodor and Smith (1982) produced a study revealing that group leaders with high power motivation create atmospheres more susceptible to groupthink.^[21][23] Leaders with high power motivation possess characteristics similar to leaders with a "closed" leadership style—an unwillingness to respect dissenting opinion. The same study indicates that level of group cohesiveness is insignificant in predicting groupthink occurrence. Park summarizes a study performed by Callaway, Marriott, and Esser (1985) in which groups with highly dominant members "made higher quality decisions, exhibited lowered state of anxiety, took more time to reach a decision, and made more statements of disagreement/agreement."^[21]:232[24] Overall, groups with highly dominant members expressed characteristics inhibitory to groupthink. If highly dominant members are considered equivalent to leaders with high power motivation, the results of Callaway, Marriott, and Esser contradict the results of Fodor and Smith. A study by Leana (1985) indicates the interaction between level of group cohesion and leadership style is completely insignificant in predicting groupthink.^[21][25] This finding refutes Janis' claim that the factors of cohesion and leadership style interact to produce groupthink. Park summarizes a study by McCauley (1989) in which structural conditions of the group were found to predict groupthink while situational conditions did not.^[10][21] The structural conditions included group insulation, group homogeneity, and promotional leadership. The situational conditions included group cohesion. These findings refute Janis' claim about group cohesiveness predicting groupthink.

Overall, studies on groupthink have largely focused on the factors (antecedents) that predict groupthink. Groupthink occurrence is often measured by number of ideas/solutions generated within a group, but there is no uniform, concrete standard by which researchers can objectively conclude groupthink occurs.^[18] The studies of groupthink and groupthink antecedents reveal a mixed body of results. Some studies indicate group cohesion and leadership style to be powerfully predictive of groupthink, while other studies indicate the insignificance of these factors. Group homogeneity and group insulation are generally supported as factors predictive of groupthink.

Case studies

Politics and military

Groupthink can have a strong hold on political decisions and military operations, which may result in enormous wastage of human and material resources. Highly qualified and experienced politicians and military commanders sometimes make very poor decisions when in a suboptimal group setting. Scholars such as Janis and Raven attribute political and military fiascoes, such as the Bay of Pigs Invasion, the Vietnam War, and the Watergate scandal, to the effect of groupthink.^[8][26] More recently, Dina Badie argued that groupthink was largely responsible for the shift in the U.S. administration's view on Saddam Hussein that eventually led to the 2003 invasion of Iraq by the United States.^[27] After the September 11 attacks, "stress, promotional leadership, and intergroup conflict" were all factors that gave rise to the occurrence of groupthink.^[27]:283 Political case studies of groupthink serve to illustrate the impact that the occurrence of groupthink can have in today's political scene.

Bay of Pigs invasion and the Cuban Missile Crisis

The United States Bay of Pigs Invasion of April 1961 was the primary case study that Janis used to formulate his theory of groupthink.^[6] The invasion plan was initiated by the Eisenhower administration, but when the Kennedy administration took over, it "uncritically accepted" the plan of the Central Intelligence Agency (CIA).^[6]:44 When some people, such as Arthur M. Schlesinger, Jr. and Senator J. William Fulbright, attempted to present their objections to the plan, the Kennedy team as a whole ignored these objections and kept believing in the morality of their plan.^[6]:46 Eventually Schlesinger minimized his own doubts, performing self-censorship.^[6]:74 The Kennedy team stereotyped Fidel Castro and the Cubans by failing to question the CIA about its many false assumptions, including the ineffectiveness of Castro's air force, the weakness of Castro's army, and the inability of Castro to quell internal uprisings.^[6]:46

Janis claimed the fiasco that ensued could have been prevented if the Kennedy administration had followed the methods to preventing groupthink adopted during the Cuban Missile Crisis, which took place just one year later in October 1962. In the latter crisis, essentially the same political leaders were involved in decision-making, but this time they learned from their previous mistake of seriously under-rating their opponents.^[6]:76

Pearl Harbor

The attack on Pearl Harbor on December 7, 1941 is a prime example of groupthink. A number of factors such as shared illusions and rationalizations contributed to the lack of precaution taken by Naval officers based in Hawaii. The United States had intercepted Japanese messages and they discovered that Japan was arming itself for an offensive attack somewhere in the Pacific Ocean. Washington took action by warning officers stationed at Pearl Harbor, but their warning was not taken seriously. They assumed that the Empire of Japan was taking measures in the event that their embassies and consulates in enemy territories were usurped.

The Navy and Army in Pearl Harbor also shared rationalizations about why an attack was unlikely. Some of them included:^[8]:83,85

• "The Japanese would never dare attempt a full-scale surprise assault against Hawaii because they would realize that it would precipitate an all-out war, which the United States would surely win."
• "The Pacific Fleet concentrated at Pearl Harbor was a major deterrent against air or naval attack."
• "Even if the Japanese were foolhardy to send their carriers to attack us [the United States], we could certainly detect and destroy them in plenty of time."
• "No warships anchored in the shallow water of Pearl Harbor could ever be sunk by torpedo bombs launched from enemy aircraft."

United States presidential election, 2016

In the weeks and months preceding the United States presidential election, 2016, there was near-unanimity among news media outlets and polling organizations that Hillary Clinton's election was extremely likely. For example, on November 7, the day before the election, The New York Times opined that Clinton then had "a consistent and clear advantage in states worth at least 270 electoral votes."^[28] The Times estimated the probability of a Clinton win at 84%.^[29] Also on November 7, Reuters estimated the probability of Clinton defeating Donald Trump in the election at 90%,^[30] and The Huffington Post put Clinton's odds of winning at 98.2% based on "9.8 million simulations."^[31]

The disconnect between the election results and the pre-election estimates, both from news media outlets and from pollsters, may have been due to two factors: political correctness, in that few news and polling professionals would admit to supporting or considering Trump as a viable candidate for fear of peer pressure; and polling error, in that a significant number of Trump supporters contacted by pollsters may have lied to or misled the pollsters—again possibly due to their fear of public opprobrium if they were identified as such.^[32]

Corporate world

In the corporate world, ineffective and suboptimal group decision-making can negatively affect the health of a company and cause a considerable amount of monetary loss.

Swissair

Aaron Hermann and Hussain Rammal illustrate the detrimental role of groupthink in the collapse of Swissair, a Swiss airline company that was thought to be so financially stable that it earned the title the "Flying Bank."^[33] The authors argue that, among other factors, Swissair carried two symptoms of groupthink: the belief that the group is invulnerable and the belief in the morality of the group.^[33]:1056 In addition, before the fiasco, the size of the company board was reduced, subsequently eliminating industrial expertise. This may have further increased the likelihood of groupthink.^[33]:1055 With the board members lacking expertise in the field and having somewhat similar background, norms, and values, the pressure to conform may have become more prominent.^[33]:1057 This phenomenon is called group homogeneity, which is an antecedent to groupthink. Together, these conditions may have contributed to the poor decision-making process that eventually led to Swissair's collapse.

Marks & Spencer and British Airways

Another example of groupthink from the corporate world is illustrated in the United Kingdom-based companies Marks & Spencer and British Airways. The negative impact of groupthink took place during the 1990s as both companies released globalization expansion strategies. Researcher Jack Eaton's content analysis of media press releases revealed that all eight symptoms of groupthink were present during this period. The most predominant symptom of groupthink was the illusion of invulnerability as both companies underestimated potential failure due to years of profitability and success during challenging markets. Up until the consequence of groupthink erupted they were considered blue chips and darlings of the London Stock Exchange. During 1998–1999 the price of Marks & Spencer shares fell from 590 to less than 300 and that of British Airways from 740 to 300. Both companies had already featured prominently in the UK press and media for more positive reasons to do with national pride in their undoubted sector-wide performance.^[34]

Sports

Recent literature of groupthink attempts to study the application of this concept beyond the framework of business and politics. One particularly relevant and popular arena in which groupthink is rarely studied is sports. The lack of literature in this area prompted Charles Koerber and Christopher Neck to begin a case-study investigation that examined the effect of groupthink on the decision of the Major League Umpires Association (MLUA) to stage a mass resignation in 1999. The decision was a failed attempt to gain a stronger negotiating stance against Major League Baseball.^[35]:21 Koerber and Neck suggest that three groupthink symptoms can be found in the decision-making process of the MLUA. First, the umpires overestimated the power that they had over the baseball league and the strength of their group's resolve. The union also exhibited some degree of closed-mindedness with the notion that MLB is the enemy. Lastly, there was the presence of self-censorship; some umpires who disagreed with the decision to resign failed to voice their dissent.^[35]:25 These factors, along with other decision-making defects, led to a decision that was suboptimal and ineffective.

Recent developments

Ubiquity model

Researcher Robert Baron (2005) contends that the connection between certain antecedents which Janis believed necessary has not been demonstrated by the current collective body of research on groupthink. He believes that Janis' antecedents for groupthink are incorrect, and argues that not only are they "not necessary to provoke the symptoms of groupthink, but that they often will not even amplify such symptoms".^[36] As an alternative to Janis' model, Baron proposed a ubiquity model of groupthink. This model provides a revised set of antecedents for groupthink, including social identification, salient norms, and low self-efficacy.

General group problem-solving (GGPS) model

Aldag and Fuller (1993) argue that the groupthink concept was based on a "small and relatively restricted sample" that became too broadly generalized.^[17] Furthermore, the concept is too rigidly staged and deterministic. Empirical support for it has also not been consistent. The authors compare groupthink model to findings presented by Maslow and Piaget; they argue that, in each case, the model incites great interest and further research that, subsequently, invalidate the original concept. Aldag and Fuller thus suggest a new model called the general group problem-solving (GGPS) model, which integrates new findings from groupthink literature and alters aspects of groupthink itself.^[17]:534 The primary difference between the GGPS model and groupthink is that the former is more value neutral and more political.^[17]:544

Reexamination

Other scholars attempt to assess the merit of groupthink by reexamining case studies that Janis had originally used to buttress his model. Roderick Kramer (1998) believed that, because scholars today have a more sophisticated set of ideas about the general decision-making process and because new and relevant information about the fiascos have surfaced over the years, a reexamination of the case studies is appropriate and necessary.^[37] He argues that new evidence does not support Janis' view that groupthink was largely responsible for President Kennedy's and President Johnson's decisions in the Bay of Pigs Invasion and U.S. escalated military involvement in the Vietnam War, respectively. Both presidents sought the advice of experts outside of their political groups more than Janis suggested.^[37]:241 Kramer also argues that the presidents were the final decision-makers of the fiascos; while determining which course of action to take, they relied more heavily on their own construals of the situations than on any group-consenting decision presented to them.^[37]:241 Kramer concludes that Janis' explanation of the two military issues is flawed and that groupthink has much less influence on group decision-making than is popularly believed to be.

Reformulation

Whyte (1998) suggests that collective efficacy plays a large role in groupthink because it causes groups to become less vigilant and to favor risks, two particular factors that characterize groups affected by groupthink.^[38] McCauley recasts aspects of groupthink's preconditions by arguing that the level of attractiveness of group members is the most prominent factor in causing poor decision-making.^[39] The results of Turner's and Pratkanis' (1991) study on social identity maintenance perspective and groupthink conclude that groupthink can be viewed as a "collective effort directed at warding off potentially negative views of the group."^[3] Together, the contributions of these scholars have brought about new understandings of groupthink that help reformulate Janis' original model.

Sociocognitive theory

According to a new theory many of the basic characteristics of groupthink – e.g., strong cohesion, indulgent atmosphere, and exclusive ethos – are the result of a special kind of mnemonic encoding (Tsoukalas, 2007). Members of tightly knit groups have a tendency to represent significant aspects of their community as episodic memories and this has a predictable influence on their group behavior and collective ideology.^[40]

Vacuum energy

From Wikipedia, the free encyclopedia

Vacuum energy is an underlying background energy that exists in space throughout the entire Universe. One contribution to the vacuum energy may be from virtual particles which are thought to be particle pairs that blink into existence and then annihilate in a timespan too short to observe. Their behavior is codified in Heisenberg's energy–time uncertainty principle. Still, the exact effect of such fleeting bits of energy is difficult to quantify. The vacuum energy is a special case of zero-point energy that relates to the quantum vacuum.^[1]

Unsolved problem in physics: Why does the zero-point energy of the vacuum not cause a large cosmological constant? What cancels it out?

The effects of vacuum energy can be experimentally observed in various phenomena such as spontaneous emission, the Casimir effect and the Lamb shift, and are thought to influence the behavior of the Universe on cosmological scales. Using the upper limit of the cosmological constant, the vacuum energy of free space has been estimated to be 10⁻⁹ joules (10⁻² ergs) per cubic meter.^[2] However, in both quantum electrodynamics (QED) and stochastic electrodynamics (SED), consistency with the principle of Lorentz covariance and with the magnitude of the Planck constant requires it to have a much larger value of 10¹¹³ joules per cubic meter.^[3][4] This huge discrepancy is known as the vacuum catastrophe.

Origin

Quantum field theory states that all fundamental fields, such as the electromagnetic field, must be quantized at each and every point in space^{[citation needed]}. A field in physics may be envisioned as if space were filled with interconnected vibrating balls and springs, and the strength of the field were like the displacement of a ball from its rest position. The theory requires "vibrations" in, or more accurately changes in the strength of, such a field to propagate as per the appropriate wave equation for the particular field in question. The second quantization of quantum field theory requires that each such ball-spring combination be quantized, that is, that the strength of the field be quantized at each point in space. Canonically, if the field at each point in space is a simple harmonic oscillator, its quantization places a quantum harmonic oscillator at each point. Excitations of the field correspond to the elementary particles of particle physics. Thus, according to the theory, even the vacuum has a vastly complex structure and all calculations of quantum field theory must be made in relation to this model of the vacuum.

The theory considers vacuum to implicitly have the same properties as a particle, such as spin or polarization in the case of light, energy, and so on. According to the theory, most of these properties cancel out on average leaving the vacuum empty in the literal sense of the word. One important exception, however, is the vacuum energy or the vacuum expectation value of the energy. The quantization of a simple harmonic oscillator requires the lowest possible energy, or zero-point energy of such an oscillator to be:
${\displaystyle {E}={\frac {1}{2}}h\nu .}$
Summing over all possible oscillators at all points in space gives an infinite quantity. To remove this infinity, one may argue that only differences in energy are physically measurable, much as the concept of potential energy has been treated in classical mechanics for centuries. This argument is the underpinning of the theory of renormalization. In all practical calculations, this is how the infinity is handled.

Vacuum energy can also be thought of in terms of virtual particles (also known as vacuum fluctuations) which are created and destroyed out of the vacuum. These particles are always created out of the vacuum in particle-antiparticle pairs, which in most cases shortly annihilate each other and disappear. However, these particles and antiparticles may interact with others before disappearing, a process which can be mapped using Feynman diagrams. Note that this method of computing vacuum energy is mathematically equivalent to having a quantum harmonic oscillator at each point and, therefore, suffers the same renormalization problems.

Additional contributions to the vacuum energy come from spontaneous symmetry breaking in quantum field theory.

Implications

Vacuum energy has a number of consequences. In 1948, Dutch physicists Hendrik B. G. Casimir and Dirk Polder predicted the existence of a tiny attractive force between closely placed metal plates due to resonances in the vacuum energy in the space between them. This is now known as the Casimir effect and has since been extensively experimentally verified. It is therefore believed that the vacuum energy is "real" in the same sense that more familiar conceptual objects such as electrons, magnetic fields, etc., are real. However, alternative explanations for the Casimir effect have since been proposed.^[5]

Other predictions are harder to verify. Vacuum fluctuations are always created as particle–antiparticle pairs. The creation of these virtual particles near the event horizon of a black hole has been hypothesized by physicist Stephen Hawking to be a mechanism for the eventual "evaporation" of black holes.^[6] If one of the pair is pulled into the black hole before this, then the other particle becomes "real" and energy/mass is essentially radiated into space from the black hole. This loss is cumulative and could result in the black hole's disappearance over time. The time required is dependent on the mass of the black hole (the equations indicate that the smaller the black hole, the more rapidly it evaporates) but could be on the order of 10¹⁰⁰ years for large solar-mass black holes.^[6]

The vacuum energy also has important consequences for physical cosmology. General relativity predicts that energy is equivalent to mass, and therefore, if the vacuum energy is "really there", it should exert a gravitational force. Essentially, a non-zero vacuum energy is expected to contribute to the cosmological constant, which affects the expansion of the universe.^{[citation needed]} In the special case of vacuum energy, general relativity stipulates that the gravitational field is proportional to ρ+3p (where ρ is the mass-energy density, and p is the pressure). Quantum theory of the vacuum further stipulates that the pressure of the zero-state vacuum energy is always negative and equal in magnitude to ρ. Thus, the total is ρ+3p = ρ-3ρ = -2ρ, a negative value. If indeed the vacuum ground state has non-zero energy, the calculation implies a repulsive gravitational field, giving rise to acceleration of the expansion of the universe,^{[citation needed]}. However, the vacuum energy is mathematically infinite without renormalization, which is based on the assumption that we can only measure energy in a relative sense, which is not true if we can observe it indirectly via the cosmological constant.^{[citation needed]}

The existence of vacuum energy is also sometimes used as theoretical justification for the possibility of free-energy machines. It has been argued that due to the broken symmetry (in QED), free energy does not violate conservation of energy, since the laws of thermodynamics only apply to equilibrium systems. However, consensus amongst physicists is that this is unknown as the nature of vacuum energy remains an unsolved problem.^[7] In particular, the second law of thermodynamics is unaffected by the existence of vacuum energy.^{[citation needed]} However, in Stochastic Electrodynamics, the energy density is taken to be a classical random noise wave field which consists of real electromagnetic noise waves propagating isotropically in all directions. The energy in such a wave field would seem to be accessible, e.g., with nothing more complicated than a directional coupler.^{[citation needed]} The most obvious difficulty appears to be the spectral distribution of the energy, which compatibility with Lorentz invariance requires to take the form Kf³, where K is a constant and f denotes frequency.^[3][8] It follows that the energy and momentum flux in this wave field only becomes significant at extremely short wavelengths where directional coupler technology is currently lacking.^{[citation needed]}

History

In 1934, Georges Lemaître used an unusual perfect-fluid equation of state to interpret the cosmological constant as due to vacuum energy. In 1948, the Casimir effect was provided an experimental method for a verification of the existence of vacuum energy, however, in 1955, Evgeny Lifshitz offered a different origin for the Casimir effect. In 1957, Lee and Yang proved the concepts of broken symmetry and parity violation, for which they won the Nobel prize. In 1973, Edward Tryon proposed the zero-energy universe hypothesis: that the Universe may be a large-scale quantum-mechanical vacuum fluctuation where positive mass-energy is balanced by negative gravitational potential energy. During the 1980s, there were many attempts to relate the fields that generate the vacuum energy to specific fields that were predicted by attempts at a Grand unification theory and to use observations of the Universe to confirm one or another version. However, the exact nature of the particles (or fields) that generate vacuum energy, with a density such as that required by inflation theory, remains a mystery.

Oxidants (Redox Reactions, including Biology)

From Wikipedia, the free encyclopedia

The two parts of a redox reaction

Rust, a slow redox reaction

A bonfire; combustion is a fast redox reaction

Sodium and fluorine bonding ionically to form sodium fluoride. Sodium loses its outer electron to give it a stable electron configuration, and this electron enters the fluorine atom exothermically. The oppositely charged ions are then attracted to each other. The sodium is oxidized, and the fluorine is reduced.

Play media

Demonstration of the reaction between a strong oxidising and a reducing agent. When few drops of glycerol (reducing agent) are added to powdered potassium permanganate (strong oxidising agent), a vigorous reaction accompanied by self-ignition starts.

Redox (short for reduction–oxidation reaction) is a chemical reaction in which the oxidation states of atoms are changed. Any such reaction involves both a reduction process and a complementary oxidation process, two key concepts involved with electron transfer processes.^[1] Redox reactions include all chemical reactions in which atoms have their oxidation state changed; in general, redox reactions involve the transfer of electrons between chemical species. The chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. It can be explained in simple terms:

• Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.
• Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.

As an example, during the combustion of wood, oxygen from the air is reduced, gaining electrons from the carbon.^[2] Although oxidation reactions are commonly associated with the formation of oxides from oxygen molecules, oxygen is not necessarily included in such reactions, as other chemical species can serve the same function.^[2]

The reaction can occur relatively slowly, as in the case of rust, or more quickly, as in the case of fire. There are simple redox processes, such as the oxidation of carbon to yield carbon dioxide (CO₂) or the reduction of carbon by hydrogen to yield methane (CH₄), and more complex processes such as the oxidation of glucose (C₆H₁₂O₆) in the human body.

Etymology

"Redox" is a portmanteau of "reduction" and "oxidation".

The word oxidation originally implied reaction with oxygen to form an oxide, since dioxygen (O₂ (g)) was historically the first recognized oxidizing agent. Later, the term was expanded to encompass oxygen-like substances that accomplished parallel chemical reactions. Ultimately, the meaning was generalized to include all processes involving loss of electrons.

The word reduction originally referred to the loss in weight upon heating a metallic ore such as a metal oxide to extract the metal. In other words, ore was "reduced" to metal. Antoine Lavoisier (1743–1794) showed that this loss of weight was due to the loss of oxygen as a gas. Later, scientists realized that the metal atom gains electrons in this process. The meaning of reduction then became generalized to include all processes involving gain of electrons. Even though "reduction" seems counter-intuitive when speaking of the gain of electrons, it might help to think of reduction as the loss of oxygen, which was its historical meaning. Since electrons are negatively charged, it is also helpful to think of this as reduction in electrical charge.

The electrochemist John Bockris has used the words electronation and deelectronation to describe reduction and oxidation processes respectively when they occur at electrodes.^[3] These words are analogous to protonation and deprotonation, but they have not been widely adopted by chemists.

The term "hydrogenation" could be used instead of reduction, since hydrogen is the reducing agent in a large number of reactions, especially in organic chemistry and biochemistry. But, unlike oxidation, which has been generalized beyond its root element, hydrogenation has maintained its specific connection to reactions that add hydrogen to another substance (e.g., the hydrogenation of unsaturated fats into saturated fats, R−CH=CH−R + H₂ → R−CH₂−CH₂−R). The word "redox" was first used in 1928.^[4]

Definitions

The processes of oxidation and reduction occur simultaneously and cannot happen independently of one another, similar to the acid–base reaction.^[2] The oxidation alone and the reduction alone are each called a half-reaction, because two half-reactions always occur together to form a whole reaction. When writing half-reactions, the gained or lost electrons are typically included explicitly in order that the half-reaction be balanced with respect to electric charge.

Though sufficient for many purposes, these general descriptions are not precisely correct. Although oxidation and reduction properly refer to a change in oxidation state — the actual transfer of electrons may never occur. The oxidation state of an atom is the fictitious charge that an atom would have if all bonds between atoms of different elements were 100% ionic. Thus, oxidation is best defined as an increase in oxidation state, and reduction as a decrease in oxidation state. In practice, the transfer of electrons will always cause a change in oxidation state, but there are many reactions that are classed as "redox" even though no electron transfer occurs (such as those involving covalent bonds).

Oxidizing and reducing agents

In redox processes, the reductant transfers electrons to the oxidant. Thus, in the reaction, the reductant or reducing agent loses electrons and is oxidized, and the oxidant or oxidizing agent gains electrons and is reduced. The pair of an oxidizing and reducing agent that are involved in a particular reaction is called a redox pair. A redox couple is a reducing species and its corresponding oxidizing form, e.g., Fe²⁺/Fe³⁺.

Oxidizers

The international pictogram for oxidizing chemicals.

Substances that have the ability to oxidize other substances (cause them to lose electrons) are said to be oxidative or oxidizing and are known as oxidizing agents, oxidants, or oxidizers. That is, the oxidant (oxidizing agent) removes electrons from another substance, and is thus itself reduced. And, because it "accepts" electrons, the oxidizing agent is also called an electron acceptor. Oxygen is the quintessential oxidizer.

Oxidants are usually chemical substances with elements in high oxidation states (e.g., H
2O
2, MnO−
4, CrO
3, Cr
2O2−
7, OsO
4), or else highly electronegative elements (O₂, F₂, Cl₂, Br₂) that can gain extra electrons by oxidizing another substance.

Reducers

Substances that have the ability to reduce other substances (cause them to gain electrons) are said to be reductive or reducing and are known as reducing agents, reductants, or reducers. The reductant (reducing agent) transfers electrons to another substance, and is thus itself oxidized. And, because it "donates" electrons, the reducing agent is also called an electron donor. Electron donors can also form charge transfer complexes with electron acceptors.

Reductants in chemistry are very diverse. Electropositive elemental metals, such as lithium, sodium, magnesium, iron, zinc, and aluminium, are good reducing agents. These metals donate or give away electrons readily. Hydride transfer reagents, such as NaBH₄ and LiAlH₄, are widely used in organic chemistry,^[5][6] primarily in the reduction of carbonyl compounds to alcohols. Another method of reduction involves the use of hydrogen gas (H₂) with a palladium, platinum, or nickel catalyst. These catalytic reductions are used primarily in the reduction of carbon-carbon double or triple bonds.

Standard electrode potentials (reduction potentials)

Each half-reaction has a standard electrode potential (E0
cell), which is equal to the potential difference or voltage at equilibrium under standard conditions of an electrochemical cell in which the cathode reaction is the half-reaction considered, and the anode is a standard hydrogen electrode where hydrogen is oxidized:

 ¹⁄₂ H₂ → H⁺ + e⁻.

The electrode potential of each half-reaction is also known as its reduction potential E0
red, or potential when the half-reaction takes place at a cathode. The reduction potential is a measure of the tendency of the oxidizing agent to be reduced. Its value is zero for H⁺ + e⁻ →  ¹⁄₂ H₂ by definition, positive for oxidizing agents stronger than H⁺ (e.g., +2.866 V for F₂) and negative for oxidizing agents that are weaker than H⁺ (e.g., −0.763 V for Zn²⁺).^[7]

For a redox reaction that takes place in a cell, the potential difference is:

E0
cell = E0
cathode – E0
anode

However, the potential of the reaction at the anode was sometimes expressed as an oxidation potential:

E0
ox = –E0
red.

The oxidation potential is a measure of the tendency of the reducing agent to be oxidized, but does not represent the physical potential at an electrode. With this notation, the cell voltage equation is written with a plus sign

E0
cell = E0
red(cathode) + E0
ox(anode)

Examples of redox reactions

Illustration of a redox reaction

A good example is the reaction between hydrogen and fluorine in which hydrogen is being oxidized and fluorine is being reduced:

H
2 + F
2 → 2 HF

We can write this overall reaction as two half-reactions:

the oxidation reaction:

H
2 → 2 H⁺ + 2 e⁻

and the reduction reaction:

F
2 + 2 e⁻ → 2 F⁻

Analyzing each half-reaction in isolation can often make the overall chemical process clearer. Because there is no net change in charge during a redox reaction, the number of electrons in excess in the oxidation reaction must equal to the number consumed by the reduction reaction (as shown above).

Elements, even in molecular form, always have an oxidation state of zero. In the first half-reaction, hydrogen is oxidized from an oxidation state of zero to an oxidation state of +1. In the second half-reaction, fluorine is reduced from an oxidation state of zero to an oxidation state of −1.

When adding the reactions together the electrons are canceled:

H 2	→	2 H+ + 2 e−
F 2 + 2 e−	→	2 F−
H2 + F2	→	2 H+ + 2 F−

And the ions combine to form hydrogen fluoride:

2 H⁺ + 2 F⁻ → 2 HF

The overall reaction is:

H
2 + F
2 → 2 HF

Metal displacement

A redox reaction is the force behind an electrochemical cell like the Galvanic cell pictured. The battery is made out of a zinc electrode in a ZnSO₄ solution connected with a wire and a porous disk to a copper electrode in a CuSO₄ solution.

In this type of reaction, a metal atom in a compound (or in a solution) is replaced by an atom of another metal. For example, copper is deposited when zinc metal is placed in a copper(II) sulfate solution:

Zn(s)+ CuSO₄(aq) → ZnSO₄(aq) + Cu(s)

In the above reaction, zinc metal displaces the copper(II) ion from copper sulfate solution and thus liberates free copper metal.

The ionic equation for this reaction is:

Zn + Cu²⁺ → Zn²⁺ + Cu

As two half-reactions, it is seen that the zinc is oxidized:

Zn → Zn²⁺ + 2 e⁻

And the copper is reduced:

Cu²⁺ + 2 e⁻ → Cu

Other examples

• The reduction of nitrate to nitrogen in the presence of an acid (denitrification):

  2 NO−
  3 + 10 e⁻ + 12 H⁺ → N₂ + 6 H₂O

• The combustion of hydrocarbons, such as in an internal combustion engine, which produces water, carbon dioxide, some partially oxidized forms such as carbon monoxide, and heat energy. Complete oxidation of materials containing carbon produces carbon dioxide.
• In organic chemistry, the stepwise oxidation of a hydrocarbon by oxygen produces water and, successively, an alcohol, an aldehyde or a ketone, a carboxylic acid, and then a peroxide.

Corrosion and rusting

Oxides, such as iron(III) oxide or rust, which consists of hydrated iron(III) oxides Fe₂O₃·nH₂O and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)₃), form when oxygen combines with other elements

Iron rusting in pyrite cubes

• The term corrosion refers to the electrochemical oxidation of metals in reaction with an oxidant such as oxygen. Rusting, the formation of iron oxides, is a well-known example of electrochemical corrosion; it forms as a result of the oxidation of iron metal. Common rust often refers to iron(III) oxide, formed in the following chemical reaction:

  4 Fe + 3 O₂ → 2 Fe₂O₃

• The oxidation of iron(II) to iron(III) by hydrogen peroxide in the presence of an acid:

  Fe²⁺ → Fe³⁺ + e⁻

  H₂O₂ + 2 e⁻ → 2 OH⁻

Overall equation:

2 Fe²⁺ + H₂O₂ + 2 H⁺ → 2 Fe³⁺ + 2 H₂O

Redox reactions in industry

Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects protected metal to a more easily corroded "sacrificial anode" to act as the anode. The sacrificial metal instead of the protected metal, then, corrodes. A common application of cathodic protection is in galvanized steel, in which a sacrificial coating of zinc on steel parts protects them from rust.

The primary process of reducing ore at high temperature to produce metals is known as smelting.

Oxidation is used in a wide variety of industries such as in the production of cleaning products and oxidizing ammonia to produce nitric acid, which is used in most fertilizers.

Redox reactions are the foundation of electrochemical cells, which can generate electrical energy or support electrosynthesis.

The process of electroplating uses redox reactions to coat objects with a thin layer of a material, as in chrome-plated automotive parts, silver plating cutlery, and gold-plated jewelry.

The production of compact discs depends on a redox reaction, which coats the disc with a thin layer of metal film.^{[clarification needed]}

Redox reactions in biology

Top: ascorbic acid (reduced form of Vitamin C)
Bottom: dehydroascorbic acid (oxidized form of Vitamin C)

Many important biological processes involve redox reactions.

Cellular respiration, for instance, is the oxidation of glucose (C₆H₁₂O₆) to CO₂ and the reduction of oxygen to water. The summary equation for cell respiration is:

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O

The process of cell respiration also depends heavily on the reduction of NAD⁺ to NADH and the reverse reaction (the oxidation of NADH to NAD⁺). Photosynthesis and cellular respiration are complementary, but photosynthesis is not the reverse of the redox reaction in cell respiration:

6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂

Biological energy is frequently stored and released by means of redox reactions. Photosynthesis involves the reduction of carbon dioxide into sugars and the oxidation of water into molecular oxygen. The reverse reaction, respiration, oxidizes sugars to produce carbon dioxide and water. As intermediate steps, the reduced carbon compounds are used to reduce nicotinamide adenine dinucleotide (NAD⁺), which then contributes to the creation of a proton gradient, which drives the synthesis of adenosine triphosphate (ATP) and is maintained by the reduction of oxygen. In animal cells, mitochondria perform similar functions. See the Membrane potential article.

Free radical reactions are redox reactions that occur as a part of homeostasis and killing microorganisms, where an electron detaches from a molecule and then reattaches almost instantaneously. Free radicals are a part of redox molecules and can become harmful to the human body if they do not reattach to the redox molecule or an antioxidant. Unsatisfied free radicals can spur the mutation of cells they encounter and are, thus, causes of cancer.

The term redox state is often used to describe the balance of GSH/GSSG, NAD⁺/NADH and NADP⁺/NADPH in a biological system such as a cell or organ. The redox state is reflected in the balance of several sets of metabolites (e.g., lactate and pyruvate, beta-hydroxybutyrate, and acetoacetate), whose interconversion is dependent on these ratios. An abnormal redox state can develop in a variety of deleterious situations, such as hypoxia, shock, and sepsis. Redox mechanism also control some cellular processes. Redox proteins and their genes must be co-located for redox regulation according to the CoRR hypothesis for the function of DNA in mitochondria and chloroplasts.

Redox cycling

A wide variety of aromatic compounds are enzymatically reduced to form free radicals that contain one more electron than their parent compounds. In general, the electron donor is any of a wide variety of flavoenzymes and their coenzymes. Once formed, these anion free radicals reduce molecular oxygen to superoxide, and regenerate the unchanged parent compound. The net reaction is the oxidation of the flavoenzyme's coenzymes and the reduction of molecular oxygen to form superoxide. This catalytic behavior has been described as futile cycle or redox cycling.

Examples of redox cycling-inducing molecules are the herbicide paraquat and other viologens and quinones such as menadione.^[8]

Redox reactions in geology

Mi Vida uranium mine, near Moab, Utah. The alternating red and white/green bands of sandstone correspond to oxidized and reduced conditions in groundwater redox chemistry.

In geology, redox is important to both the formation of minerals and the mobilization of minerals, and is also important in some depositional environments. In general, the redox state of most rocks can be seen in the color of the rock. The rock forms in oxidizing conditions, giving it a red color. It is then "bleached" to a green—or sometimes white—form when a reducing fluid passes through the rock. The reduced fluid can also carry uranium-bearing minerals. Famous examples of redox conditions affecting geological processes include uranium deposits and Moqui marbles.

Balancing redox reactions

Describing the overall electrochemical reaction for a redox process requires a balancing of the component half-reactions for oxidation and reduction. In general, for reactions in aqueous solution, this involves adding H⁺, OH⁻, H₂O, and electrons to compensate for the oxidation changes.

Acidic media

In acidic media, H⁺ ions and water are added to half-reactions to balance the overall reaction.
For instance, when manganese(II) reacts with sodium bismuthate:

Unbalanced reaction:	Mn2+(aq) + NaBiO3(s) → Bi3+(aq) + MnO− 4 (aq)
Oxidation:	4 H2O(l) + Mn2+(aq) → MnO− 4(aq) + 8 H+(aq) + 5 e−
Reduction:	2 e− + 6 H+ + BiO− 3(s) → Bi3+(aq) + 3 H2O(l)

The reaction is balanced by scaling the two half-cell reactions to involve the same number of electrons (multiplying the oxidation reaction by the number of electrons in the reduction step and vice versa):

8 H₂O(l) + 2 Mn²⁺(aq) → 2 MnO−
4(aq) + 16 H⁺(aq) + 10 e⁻

10 e⁻ + 30 H⁺ + 5 BiO−
3(s) → 5 Bi³⁺(aq) + 15 H₂O(l)

Adding these two reactions eliminates the electrons terms and yields the balanced reaction:

14 H⁺(aq) + 2 Mn²⁺(aq) + 5 NaBiO₃(s) → 7 H₂O(l) + 2 MnO−
4(aq) + 5 Bi³⁺(aq) + 5 Na+(aq)

Basic media

In basic media, OH⁻ ions and water are added to half reactions to balance the overall reaction.

For example, in the reaction between potassium permanganate and sodium sulfite:

Unbalanced reaction:	KMnO4 + Na2SO3 + H2O → MnO2 + Na2SO4 + KOH
Reduction:	3 e− + 2 H2O + MnO− 4 → MnO2 + 4 OH−
Oxidation:	2 OH− + SO2− 3 → SO2− 4 + H2O + 2 e−

Balancing the number of electrons in the two half-cell reactions gives:

6 e⁻ + 4 H₂O + 2 MnO−
4 → 2 MnO₂ + 8 OH⁻

6 OH⁻ + 3 SO2−
3 → 3 SO2−
4 + 3 H₂O + 6 e⁻

Adding these two half-cell reactions together gives the balanced equation:

2 KMnO₄ + 3 Na₂SO₃ + H₂O → 2 MnO₂ + 3 Na₂SO₄ + 2 KOH

Memory aids

The key terms involved in redox are often confusing to students.^[9][10] For example, an element that is oxidized loses electrons; however, that element is referred to as the reducing agent. Likewise, an element that is reduced gains electrons and is referred to as the oxidizing agent.^[11] Acronyms or mnemonics are commonly used^[12] to help remember the terminology:

• "OIL RIG" — oxidation is loss of electrons, reduction is gain of electrons.^{[9][10][11][12]}
• "LEO the lion says GER" — loss of electrons is oxidation, gain of electrons is reduction.^{[9][10][11][12]}
• "LEORA says GEROA" — loss of electrons is oxidation (reducing agent), gain of electrons is reduction (oxidizing agent).^[11]
• "RED CAT" and "AN OX", or "AnOx RedCat" ("an ox-red cat") — reduction occurs at the cathode and the anode is for oxidation.
• "RED CAT gains what AN OX loses" – reduction at the cathode gains (electrons) what anode oxidation loses (electrons).