61) A researcher needs 5.00 mg of 128Ba for an experiment. If the half-life of 128Ba is 2.43 days, how many milligrams of 128BaCl2 must she order from the manufacturer if it takes 4.50 days to ship the material from the manufacturer to the university? (Assume the molar mass of 128Ba is 128 g/mol.)
A) 11.6 mg
B) 18.0 mg
C) 21.5 mg
D) 44.9 mg
62) A plot of 1/[BrO–] vs time is linear for the reaction:
3 BrO–(aq) → BrO3–(aq) + 2 Br–(aq)
What is the order of the reaction with respect to the hypobromite ion, BrO–?
63) In aqueous solution, hypobromite ion, BrO–, reacts to produce bromate ion, BrO3–, and bromide ion, Br–, according to the following chemical equation.
3 BrO–(aq) → BrO3–(aq) + 2 Br–(aq)
A plot of 1/[BrO–] vs. time is linear and the slope is equal to 0.056 M-1s-1. If the initial concentration of BrO– is 0.80 M, how long will it take one-half of the BrO– ion to react?
A) 4.5 × 10-2 s
B) 7.1 s
C) 12 s
D) 22 s
64) The second-order reaction, 2 Mn(CO)5 → Mn2(CO)10 has a rate constant equal to 3.0 × 109 M-1s-1 at 25°C. If the initial concentration of Mn(CO)5 is 1.0 × 10-5 M, how long will it take for 90.% of the reactant to disappear?
A) 3.3 × 10-16 s
B) 3.7 × 10-15 s
C) 3.0 × 10-4 s
D) 3.0 × 103 s
65) Nitrogen dioxide decomposes at 300°C via a second-order process to produce nitrogen monoxide and oxygen according to the following chemical equation.
2 NO2(g) → 2 NO(g) + O2(g).
A sample of NO2(g) is initially placed in a 2.50-L reaction vessel at 300°C. If the half-life and the rate constant at 300°C are 11 seconds and 0.54 M-1 s-1, respectively, how many moles of NO2 were in the original sample?
A) 0.17 mol
B) 0.42 mol
C) 5.9 mol
D) 15 mol
66) Hydrogen iodide decomposes at 800 K via a second-order process to produce hydrogen and iodine according to the following chemical equation.
2 HI(g) → H2(g) + I2(g)
At 800 K it takes 142 seconds for the initial concentration of HI to decrease from 6.75 × 10-2 M to 3.50 × 10-2 M. What is the rate constant for the reaction at this temperature?
A) 5.12 × 10-4 M-1s-1
B) 9.69 × 10-2 M-1s-1
C) 10.3 M-1s-1
D) 1.95 × 103 M-1s-1
67) The reaction: 2 HI → H2 + I2, is second order and the rate constant at 800 K is 9.70 × 10-2 M-1 s-1. How long will it take for 8.00 × 10-2 mol/L of HI to decrease to one-fourth of its initial concentration?
A) 0.619 s
B) 124 s
C) 387 s
D) 429 s
68) Which statement below regarding the half-life of a second-order reaction is true?
A) Each half-life is half as long as the preceding one.
B) Each half-life is twice as long as the preceding one.
C) Each half-life is four times as long as the preceding one.
D) The length of the half-life remains unchanged throughout the course of the reaction.
69) For the hypothetical second order reaction: A → products, the general rate law is: rate = k[A]2. How long is the third half-life of the reaction if [A]0 is 0.080 M and the first half-life is 22 minutes?
A) 0.57 min
B) 1.7 min
C) 7.3 min
D) 88 min
70) If the units for rate are M s-1, what are the units for the rate constant, k, for a zeroth-order reaction?
C) M s-1
D) M-1 s-1
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