January 22, 2017

Homework Help: Chemistry

Posted by Neha on Sunday, November 13, 2011 at 1:17pm.

The iodide ion can be oxidized in an acidic solution by hydrogen peroxide. One proposed
mechanism for the reaction is as follows:
Step 1: H2O2 (aq) + I-(aq) → H2O (l) + OI-(aq) slow

Step 2: H+(aq) + OI-(aq) → HOI(aq) fast

Step 3: HOI (aq) + H+(aq) + I-(aq) → I2 (aq) + H2O (l) fast

A. Write the overall equation for the reaction.
B. What are the rate law and molecularity for each step?
C. What is the overall rate law for the reaction?

Nitric oxide (NO) is one of the by-products of the high-temperature combustion of
gasoline in automobiles. Nitric oxide reacts with oxygen to produce nitrogen dioxide in
the atmosphere, which eventually leads to a degradation of the ozone layer through
reactions of nitrogen dioxide and ozone. The reaction between nitric oxide and oxygen
is second-order for nitric oxide and first-order for oxygen. Below are three proposed
mechanisms for this reaction:
I. 2 NO (g) + O2 (g) → 2 NO2 (g)
II. 2 NO (g) <--> N2O2 (g) fast
N2O2 (g) + O2 (g) → 2 NO2 (g) slow
III. 2 NO (g) <--> N2 (g) + O2 (g) fast
N2 (g) + 2 O2 (g) → 2 NO2 (g) slow

A. Write the rate law and determine the molecularity for each step for the three
proposed mechanisms.
B. Write the overall rate law for each of the proposed mechanisms.
C. The experimentally determined rate law for the reaction is rate = k[NO]^2
[O2]. Which of the three proposed mechanisms is the best choice for the actual mechanism? Why?

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