Emotional appeals are usually related to persuasion, not to exposition. Emotional appeals are usually not appropriate for straight information-transfer which aims at the rational, logical, and cognitive aspects of the audience.

However, if you do use an emotional appeal in expository writing, it should be a very conscious decision on your part, not accidental, one you can defend or justify.

Otherwise you are open to criticism, for example, if you present information using slanted or biased language (emotionally loaded words) or half-truth arguments ("stacking the deck," omitting relevant valid counter-arguments). Some people do this unintentionally or accidentally. For example, a political advocate or a religious zealot may not realize that some words used commonly within one group may seem biased to outsiders.

Although an emotional appeal in an expository essay may attract attention, it is usually the wrong kind of attention, and is likely to be rejected, in exposition and in rational arguments, as a fallacy.

Traditional names for the common emotional fallacies include: ad hominum (an attack against the person rather than the argument, name-calling, character assassination); ad misericordium (an emotional appeal for pity or sympathy, a tearjerker), and ad populum ("to the people"), a general term for any emotional appeal to the audience's desires or fears.

Notice that what is condemned in rational argument as a logical fallacy is often the core of nonrational persuasion as commonly seen in ads and much political rhetoric.

Anytime you are writing on a controversial topic, or a deeply felt issue in which you have an emotional involvement, get another person to check your writing for any bias which might distract your audience, or weaken your case.