AP Chemistry · Topic 9.6
Coupled Reactions Practice
Part of Applications of Thermodynamics.(ENE-5.C)
Practice questions
3
Sample questions
3 of 3 — sign in to practice the rest with adaptive difficulty and mastery tracking.
Sample 1difficulty 4/5
What is ΔG for the coupled reaction?
- A
0 kJ
- Bcheck_circle
-15 kJ
- C
+35 kJ
- D
+15 kJ
Why
ΔG_total = (+10) + (-25) = -15 kJ; the net reaction is spontaneous when coupled.
- A
Sample 2difficulty 4/5
ATP hydrolysis (ΔG° ≈ −31 kJ/mol) drives many non-spontaneous reactions in cells via
- A
Heat transfer only
- Bcheck_circle
Coupling — sum of ΔG's becomes negative
- C
Photolysis
- D
Catalysis without thermodynamics
Why
Energetic coupling: a strongly negative ΔG reaction shares its drop with a non-spontaneous one.
- A
Sample 3difficulty 4/5
A non-spontaneous reaction with ΔG = +30 kJ can be driven if coupled to a reaction with
- A
ΔH = 0
- B
ΔS = 0
- Ccheck_circle
ΔG = −50 kJ
- D
ΔG = +50 kJ
Why
Sum must be negative. +30 + (−50) = −20 kJ; coupled ΔG of −50 drives it.
- A