AP Chemistry · Topic 9.4
Thermodynamic and Kinetic Control Practice
Part of Applications of Thermodynamics.(ENE-4.D)
Practice questions
3
Sample questions
3 of 3 — sign in to practice the rest with adaptive difficulty and mastery tracking.
Sample 1difficulty 3/5
A reaction has ΔH > 0 and ΔS > 0. It is spontaneous at
- A
All T
- Bcheck_circle
High T only
- C
Never
- D
Low T only
Why
TΔS must overcome positive ΔH; this happens only at sufficiently high T.
- A
Sample 2difficulty 3/5
A spontaneous reaction
- A
Must be fast
- B
Has Eₐ = 0
- Ccheck_circle
May be very slow (ΔG only tells direction, not speed)
- D
Has ΔH = 0
Why
Diamond → graphite has ΔG < 0 yet is essentially infinitely slow at room T.
- A
Sample 3difficulty 4/5
Reaction with ΔH < 0 and ΔS < 0 becomes non-spontaneous when
- A
Never
- B
Always
- C
T < ΔH/ΔS
- Dcheck_circle
T > ΔH/ΔS
Why
ΔG = ΔH − TΔS; both are negative, so eventually large T makes −TΔS positive enough → ΔG > 0.
- A