AP Chemistry · Topic 5.1
Reaction Rates Practice
Part of Kinetics.(TRA-3.A)
Practice questions
6
Sample questions
5 of 6 — sign in to practice the rest with adaptive difficulty and mastery tracking.
Sample 1difficulty 2/5
The dashed line shows the average rate from t=0 to t=tf. As the time interval shrinks toward zero, the chord slope approaches:
- A
The rate constant k
- B
Infinity
- Ccheck_circle
The instantaneous rate
- D
Zero
Why
Limit of average rate as Δt -> 0 is the instantaneous rate at that time.
- A
Sample 2difficulty 2/5
Which is true for a reaction with rate decreasing over time?
- A
Rate increases as products form
- B
Average rate equals initial rate
- Ccheck_circle
Instantaneous rate at t=0 is largest
- D
Rate is independent of concentration
Why
Reactant concentration is highest at t=0, so initial instantaneous rate is largest.
- A
Sample 3difficulty 2/5
A common technique to follow a gas-producing reaction's rate is
- A
Measure color of catalyst
- B
Measure pH continuously
- Ccheck_circle
Measure mass loss or gas volume vs time
- D
Measure ΔH directly
Why
For gas products, monitor mass decrease (open container) or gas volume produced over time.
- A
Sample 4difficulty 2/5
For 2 N2O5 -> 4 NO2 + O2, [N2O5] is consumed twice as fast (in moles) as O2 is produced.
The rate of formation of NO2 equals what multiple of the rate of disappearance of N2O5?
- A
4×
- Bcheck_circle
2×
- C
1×
- D
1/2×
Why
Stoichiometry: 2 N2O5 -> 4 NO2. So [NO2] forms at twice the rate that [N2O5] is consumed.
- A
Sample 5difficulty 2/5
For 2 NO₂ → 2 NO + O₂, if [NO₂] decreases at 0.080 M/s, the rate of formation of O₂ is
- A
0.080 M/s
- B
0.020 M/s
- Ccheck_circle
0.040 M/s
- D
0.160 M/s
Why
Rate = (1/2)·d[NO₂]/dt = d[O₂]/dt → O₂ rate = 0.040 M/s.
- A