Chemistry Free Energy and Entropy Quiz

A system is in a highly ordered state (low entropy). Which of the following actions will most likely increase the entropy of the system?

• Cooling the system down

• Crystallizing a solution

• Melting the solid phase into a liquid

• Decreasing the number of gas particles

A reaction has a negative enthalpy change (ΔH < 0) and a positive entropy change (ΔS > 0). Which of the following can be inferred?

• The reaction is nonspontaneous at all temperatures.

• The reaction is spontaneous only at high temperatures.

• The reaction is spontaneous at all temperatures.

• The reaction is nonspontaneous at low temperatures.

Why does adding salt to water increase the system's entropy?

• It decreases the number of particles.

• It increases disorder as ions disperse in the solution.

• It causes water to freeze, decreasing molecular motion.

• It decreases energy distribution in the system.

A certain reaction is observed to be spontaneous at low temperatures but nonspontaneous at high temperatures. What is likely true about this reaction?

• ΔH > 0, ΔS > 0

• ΔH > 0, ΔS < 0

• ΔH < 0, ΔS > 0

• ΔH < 0, ΔS < 0

Ice melting at room temperature is considered a spontaneous process because:

• Entropy decreases, and energy is absorbed.

• Enthalpy increases, and entropy decreases.

• Entropy increases, and free energy decreases.

• Free energy remains constant.

At what condition does a reaction with ΔH > 0 and ΔS > 0 become thermodynamically favorable?

• At high temperatures

• At low temperatures

• At all temperatures

• Never

Which of the following represents a spontaneous process?

• Compressing a gas

• Melting of ice at -5°C

• Rusting of iron in moist air

• Freezing water at room temperature

The gas spontaneously expands in a vacuum. What drives this process?

• Decrease in enthalpy

• Increase in entropy

• Decrease in temperature

• Increase in free energy

If ΔG = 0 for a given reaction, which of the following statements is true?

• The reaction is at equilibrium.

• The reaction is nonspontaneous.

• The reaction has ceased to occur.

• Entropy is zero.

Increasing temperature is likely to make which type of reaction favorable?

• ΔH < 0, ΔS < 0

• ΔH > 0, ΔS > 0

• ΔH < 0, ΔS > 0

• ΔH > 0, ΔS < 0