Quiz: Gibbs Free Energy

1. The thermodynamic quantity that combines enthalpy and entropy is
a. maximum enthalpy
b. grand entropy
c. free energy
2. In order to combine enthalpy and entropy, entropy must be first
a. added to the mass of the species
b. multiplied by the temperature of the reaction in Kelvin
c. divided by the volume of the species
3. The sign of Δ G predicts whether the formation of the products in a reaction is favored. If the value is positive, the formation of the products in a reaction is
a. not favored
b. favored
c. favored some of the time
4. The Δ G value for the formation of gaseous water at 25°C and 1.0 atm is −228 kJ/mol. The formation of gaseous water at these conditions is
a. occasionally spontaneous
b. always spontaneous
c. never spontaneous

Use the following data to answer questions 5–7. The reaction is: equation

  PCl3( g) Cl2( g) PCl5( g)
Δ Hfo(kJ/mol) –287.0 0 –374.9
Sfo(J/mol) 331.78 223.07 364.6
Δ Gfo (kJ/mol) –267.8 0 –305.0

5. Calculate the Δ H and Δ S for this reaction at 298 K.
a. 87.9 kJ, –0.19025 J/K
b. 87.9 kJ, 0.19025 J/K
c. –87.9 kJ, –0.19025 J/K
6. Calculate the Δ G for this reaction at 298 K.
a. –37.2 kJ
b. –138.6 kJ
c. 37.2 kJ
7. The reaction will exhibit what type of behavior at 298 K?
a. never spontaneous
b. always spontaneous
c. is at equilibrium

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