Free Printable AP Chemistry Entropy and Gibbs Free Energy

Worksheets

AP Chemistry Entropy and Gibbs Free Energy

Total questions: 20

Worksheet time: 19mins

Name

Class

Date

Which process is accompanied by a decrease in entropy?

boiling of water

condensing of water vapor

subliming of iodine

melting of ice

Systems in nature tend to undergo changes toward

lower energy and less disorder

lower energy and more disorder

higher energy and less disorder

higher energy and more disorder

Given the change of phase:

CO₂(g) —> CO₂(s)

As CO₂(g) changes to CO₂(s), the entropy of the system

decreases

increases

remains the same

Which phase change represents a decrease in entropy?

solid to liquid

gas to liquid

liquid to gas

solid to gas

Which one of these would result in a decrease in entropy?

A solid solute dissolves in water.

A gas is released.

A liquid freezes.

A liquid boils.

Entropy always increases when

enthalpy decreases.

temperature decreases.

temperature increases.

volume increases.

Spontaneous reactions are driven by

increasing enthalpy and increasing entropy.

decreasing enthalpy and decreasing entropy.

increasing enthalpy and decreasing entropy.

decreasing enthalpy and increasing entropy.

Solid magnesium dissolves in a hydrochloric acid, releasing hydrogen gas and heat from a solution of magnesium chloride. What is the sign on ΔH for this reaction?

Negative because it is exothermic

Negative because it is endothermic

Positive because it is exothermic

Positive because it is endothermic

Solid magnesium dissolves in a hydrochloric acid, releasing hydrogen gas and heat from a solution of magnesium chloride. What is the sign on ΔS for this reaction?

Negative because it is becoming more ordered.

Negative because it is becoming more disordered.

Positive because it is becoming more ordered.

Positive because it is becoming more disordered.

10.

A reaction has a positive ΔH and a positive ΔS. Which of the following is true?

It will be spontaneous at all temperatures.

It will be nonspontaneous at all temperatures.

It will be spontaneous at low temperatures.

It will be spontaneous at high temperatures.

11.

Entropy increases from solid, liquid to gas. Why?

Molecular disorder increases

Molecular randomness decreases

Molecules are more energetic

Molecules are more reactive

12.

Solid magnesium dissolves in a hydrochloric acid, releasing hydrogen gas and heat from a solution of magnesium chloride. What is the sign on ΔG for this reaction?

Negative because it is spontaneous

Negative because it is nonspontaneous

Positive because it is spontaneous

Positive because it is nonspontaneous

13.

Identify whether the following result in an increase or decrease in entropy:

3 moles of gas (on reactant side) --> 6 moles of gas (product)

increase

decrease

14.

What type of reaction is shown in the reaction pathway?

endothermic reaction

exothermic reaction

15.

ΔH value in an endothermic reaction is a positive number.

True

False

16.

The reaction
A + 2 B₂ + C --> CAB₄
has an enthalpy change of -104 kJ and a change in entropy of -60.8 J/K at 30 °C. What is the free energy and spontaneity of the reaction?

-85.6 kJ, spontaneous

-18.3 kJ, not spontaneous

+18.3 kJ, spontaneous

+85.6 kJ, not spontaneous

17.

True/False: The rate of a chemical reaction is unrelated to the spontaneity of the reaction.

True

False

18.

When a liquid boils what are the signs for Δ H and Δ S ? (Think about H₂O as an example!)

Δ H = + Δ S = +

Δ H = - Δ S = -

Δ H = + Δ S = -

Δ H = - Δ S = +

19.

Predict the signs of Δ H , Δ S and Δ G for the reaction:

Mg(s) → Mg(g)

Δ H= - , Δ S = + and Δ G = - (all temps)

Δ H= + , Δ S = + and Δ G = - (At all temps)

Δ H= + , Δ S = + and Δ G = - (At low temps)

Δ H= + , Δ S = + and Δ G = - (At high temps)

20.

What signs of Δ H and Δ S will always yield a reaction that is non-spontaneous ? (Think of the equation for ΔG°!!)