Question

The iodate ion, IO₃⁻, is reduced by sulfite, SO₃²⁻, according to the following net ionic equation:
$IO_3^- (aq) + 3SO_3^{2-} (aq) \rightarrow I^-(aq) + 3SO_4^{2-}(aq)$.
The reaction is found to be first order in IO₃⁻, first order in SO₃²⁻, and first order in H⁺. If [IO₃⁻]=x, [SO₃²⁻]=y, and [H⁺]=z.
1) By what factor will the rate of the reaction change if the pH decreases from 6.50 to 2.00?
2) The reaction is pH dependent even though the H⁺ ion does not appear in the overall reaction. Which of the following explains this observation?
a. H⁺ is an intermediate in the reaction mechanism.
b.The exponent of [H⁺] in the rate law is zero.
c. H⁺ serves as a catalyst in the reaction.
d. H⁺ enters the reaction mechanism after the rate-determining step.

Answer 1

Answer:

〖10〗^(-2)/〖10〗^(-6.5)

H + is an intermediary in the reaction mechanism

Explanation:

Hi!

If the pH decreases the concentration of hydrogen ion increases. Being the first order reaction in H + the velocity varies by the same magnitude.

The reaction occurs in acidic medium and the hydrogen ion is necessary. However, H + is not a catalyst because it is consumed during the reaction and does not return to its initial form.

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