HW Ch 18: Part B

How does the molar entropy of a substance change with increasing temperature?

The molar entropy of a substance...

• decreases with increasing temperature because the substance can access more energy levels.

• increases with increasing temperature because the substance can access fewer energy levels.

• increases with increasing temperature because the substance can access more energy levels.

• decreases with increasing temperature because the substance can access fewer energy levels.

Predict the conditions (high temperature, low temperature, all temperatures, or no temperatures) under which each reaction is spontaneous.

Drag the appropriate items to their respective bins.

Groups:

(a) High Temperature

,

(b) Low Temperature

• 
• 
• 
• 

Calculate ΔG°_rxn at −55.0°C.

Express the free energy change to three significant figures and include the appropriate units.

ΔG°_rxn = ___ Unit

Answer explanation

Is the reaction more spontaneous (more negative ΔG°_rxn) or less spontaneous (more positive ΔG°_rxn) at a lower temperature?

• more spontaneous

• less spontaneous

Consider the oxidation of NO to NO2:

NO (g) + 12O2 (g) → NO2 (g)

Calculate ΔG°_rxn at 25°C

Express the free energy change in kilojoules to three significant figures.

ΔG°_rxn = ___ kJ

Answer explanation

Consider the oxidation of NO to NO2:

NO (g) + 1/2 O2 (g) → NO2 (g)

Specify whether the reaction is spontaneous at standard conditions.

The reaction is ____ at standard conditions.

• spontaneous

• at equilibrium

• nonspontaneous

298 K

Express your answer in kilojoules to three significant figures.

ΔG° = ___ kJ

Answer explanation

721 K

Express your answer in kilojoules to three significant figures.

ΔG° = ___ kJ

Answer explanation

860 K

Express your answer in kilojoules to two significant figures.

ΔG° = __ kJ

Answer explanation

Indicate whether the reaction is spontaneous or nonspontaneous at each temperature.

Drag the appropriate items to their respective bins.

Groups:

(a) spontaneous

,

(b) nonspontaneous

• reaction at 721K (-10.5kJ)

• reaction at 298K (-72.5)

• reaction at 860K (9.9kJ)