# Quiz | Chemical Thermodynamics

1

Which of the following statements best describes the Second Law of Thermodynamics?

Second Law of Thermodynamics: the total entropy of an isolated system can never decrease over time and is constant if all processes are reversible ⇒ the entropy change is never negative: ΔSsystem + ΔSsurrounding ≥ 0

2

What is the expression of the Gibbs energy change?

3

Which of the following criteria for reaction spontaneity is incorrect?

ΔGrxn = RT ln $\left(\frac{\mathrm{Q}}{\mathrm{K}}\right)$

Gibbs criteria for reaction spontaneity:
If Q < K  ⇔  ΔGrxn < 0: reaction proceeds spontaneously from left to right
If Q > K  ⇔  ΔGrxn > 0: reaction proceeds spontaneously from right to left
If Q = K  ⇔  ΔGrxn = 0: reaction is at equilibrium

4

Which of the following statements is always true when a reversible chemical reaction has attained equilibrium?

5

What is the relationship between the equilibrium constant K and the temperature T?

ln K = - $\frac{∆{{\mathrm{H}}^{0}}_{\mathrm{rxn}}}{\mathrm{RT}}$$\frac{∆{{\mathrm{S}}^{0}}_{\mathrm{rxn}}}{\mathrm{R}}$ ⇒ a plot of ln K versus $\frac{1}{\mathrm{T}}$ is linear (ln K and $\frac{1}{\mathrm{T}}$ are proportional)

6

When does the entropy usually increase?

Entropy S is a measure of the amount of disorder in a system ⇒ the greater the disorder the higher the entropy.
The disorder of a system is greatest when a molecule is broken into 2 or more molecules or when a solid turns into a liquid or when a liquid turns into a gas