206 ❯ STEP 4. Review the Knowledge You Need to Score High
- The rate law for the following reaction is Rate =
k[H 2 ] [I 2 ]. The reaction is H 2 (g) + I 2 (g) → 2
HI(g). A chemist studying this reaction prepared
what he thought was a mixture that was 0.10 M
in H 2 and 0.20 M in I 2. The mixture actually
had a slightly higher I 2 concentration. All other
reaction conditions were correct. Because of the
error, the experiment did not proceed exactly
as expected. Which of the following statements
is true about the actual experiment (higher I 2 )
relative to the experiment the chemist thought he
was performing (expected I 2 )?
(A) The values of k and the reaction rate both
decreased.
(B) The values of k and the reaction rate both
increased.
(C) The value of the rate increased, but k
remained the same.
(D) The value of k increased, but the reaction
rate remained the same. - Step 1: 2 NO 2 (g) → N 2 (g) + 2 O 2 (g)
Step 2: 2 CO(g) + O 2 (g) → 2 CO 2 (g)
Step 3: N 2 (g) + O 2 (g) → 2 NO(g)
The above is a proposed mechanism for the
reaction of NO 2 and CO. What are the overall
products of the reaction?
(A) NO and CO 2
(B) O 2 and CO 2
(C) N 2 and NO
(D) NO and O 2
16. The reaction of bromine, Br 2 , with nitrogen
oxide, NO, is Br 2 (g) + 2 NO(g) →2 NOBr(g).For this reaction, the observed rate law is Rate =
k [Br 2 ] [NO]^2. Why is the following unlikely to
be in the mechanism?
Br 2 (g) + 2 NO(g) → 2 NOBr(g)
(A) NO is an unstable molecule.
(B) Br 2 is too stable to react.
(C) This is a ternary step.
(D) This could be a step in the mechanism.