CHEM 102 – Winter 18 Exam 2 Review Practice Problems
1) Which substance in the reaction below either appears or disappears
the slowest? C2H4(g) + 3 O2(g) 🡒 2 CO2(g) + 2 H2O
A) C2H4
B) O2
C) CO2
D) H2O
E) The rates of appearance and disappearance are the same for all of these.
2) In the reaction 2A + B → 2C + D, -Δ[A]/Δt is found to be 5.0 M ∙ min−1. What
is the rate of reaction of B?
A) 2.5
B) 5.0
C) 10
D) 75
E) Additional information is required.
3) For a first-order reaction, the rate constant, k, could have the following units.
A) min
B) min−1
C) mol L−1 min−1
D) min mol L−1
E) L mol−1
4) The decomposition of nitrogen dioxide to nitrogen and oxygen is second
order with a rate constant, k = 12.5 M−1 s−1. What is the half-life for the
reaction if [NO2]0 = 0.00260 M?
A) 10.6 s
B) 22.8 s
C) 30.8 s
D) 42.4 s
E) 68.4 s
5) The half-life of cesium-130 is 30 minutes. What percentage of the initial
activity will be present after 2.0 hours, assuming radioactive decay occurs by
a first order rate mechanism?
A) 50
, B) 25
C) 12.5
D) 6.25
E) 3.13
1) Which substance in the reaction below either appears or disappears
the slowest? C2H4(g) + 3 O2(g) 🡒 2 CO2(g) + 2 H2O
A) C2H4
B) O2
C) CO2
D) H2O
E) The rates of appearance and disappearance are the same for all of these.
2) In the reaction 2A + B → 2C + D, -Δ[A]/Δt is found to be 5.0 M ∙ min−1. What
is the rate of reaction of B?
A) 2.5
B) 5.0
C) 10
D) 75
E) Additional information is required.
3) For a first-order reaction, the rate constant, k, could have the following units.
A) min
B) min−1
C) mol L−1 min−1
D) min mol L−1
E) L mol−1
4) The decomposition of nitrogen dioxide to nitrogen and oxygen is second
order with a rate constant, k = 12.5 M−1 s−1. What is the half-life for the
reaction if [NO2]0 = 0.00260 M?
A) 10.6 s
B) 22.8 s
C) 30.8 s
D) 42.4 s
E) 68.4 s
5) The half-life of cesium-130 is 30 minutes. What percentage of the initial
activity will be present after 2.0 hours, assuming radioactive decay occurs by
a first order rate mechanism?
A) 50
, B) 25
C) 12.5
D) 6.25
E) 3.13
