Calculate the change in Gibbs free energy for each of the following sets of ? H

Question

Calculate the change in Gibbs free energy for each of the following sets of ?Hrxn, ?Srxn, and T.

Part A

?H?rxn= 86 kJ , ?Srxn= 147 J/K , T= 300 K

Express your answer using two significant figures.

Predict whether or not the reaction in part A will be spontaneous at the temperature indicated.

Part B

?H?rxn= 86 kJ , ?Srxn= 147 J/K , T= 757 K

Express your answer using two significant figures.

Predict whether or not the reaction in part B will be spontaneous at the temperature indicated.

Part C

?H?rxn= 86 kJ , ?Srxn=? 147 J/K , T= 300 K

Express your answer using two significant figures.

Predict whether or not the reaction in part C will be spontaneous at the temperature indicated.

Part D

?H?rxn=? 86 kJ , ?Srxn= 147 J/K , T= 393 K

Express your answer using two significant figures.

Predict whether or not the reaction in part D will be spontaneous at the temperature indicated.

Explanation / Answer

A)
?Ho = 86.0 KJ
?So = 147 J/K
= 0.147 KJ/K
T = 300 K

use:
?Go = ?Ho - T*?So
?Go = 86.0 - 300.0 * 0.147
?Go = 41.9 KJ
Answer: 42 KJ

B)
?Ho = 86.0 KJ
?So = 147 J/K
= 0.147 KJ/K
T = 757 K

use:
?Go = ?Ho - T*?So
?Go = 86.0 - 757.0 * 0.147
?Go = -25.279 KJ
Answer: -25 KJ

C)
?Ho = 86.0 KJ
?So = -147 J/K
= -0.147 KJ/K
T = 300 K

use:
?Go = ?Ho - T*?So
?Go = 86.0 - 300.0 * -0.147
?Go = 130.1 KJ
Answer: 130 KJ

D)
?Ho = -86.0 KJ
?So = 147 J/K
= 0.147 KJ/K
T = 393 K

use:
?Go = ?Ho - T*?So
?Go = -86.0 - 393 * 0.147
?Go = -143.771 KJ
Answer: -1.44*10^2 KJ/mol

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