AP Chemistry : Entropy

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

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Example Question #11 : Entropy

A reaction will reach equilibrium when the system's entropy __________.

Possible Answers:

is zero

is at a minimum

is at a maximum

entropy does not influence equilibrium at all

Correct answer:

is at a maximum

Explanation:

Equilibrium is the basis of entropy, which can essentially be thought of as the distribution of energy in the system. For a reaction at a given temperature, the system's entropy will be at a maximum when it reaches equilbrium because this is the ideal energy state, and the forward and reverse reactions are occurring at a steady rate.

Example Question #11 : Entropy

Consider the following reaction:

Below is a list of the standard entropy of formation for the compounds in the reaction:

What is the entropy of the reaction when one mole of ammonia is formed?

Possible Answers:

Correct answer:

Explanation:

Since we have the entropies of formation, we can find the entropy of the reaction using the following equation:

We will need to use the coefficients from the balanced equation to calculate the entropy.

Since this is the entropy for the reaction when two moles of ammonia are formed, we must divide this entropy by two in order to solve for the entropy of one mole.

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