The decomposition of hydrogen peroxide in solution and in the presence of iodide ion was studied in laboratory, and the following mechanism proposed based on the experimental data.
H2O2 + I - = H2O + IO - (slow)
H2O2 + IO - = H2O + O2 + I - (fast)
Which one of the following statements is false? Choose answer (E) if more than one or none are false.
a. The reaction is first order with respect to H2O2.
b. The reaction is first order with respect to I -
c. I - is a catalyst.
d. IO - is an intermediate.
e. More than one the above statements is false (or none of the statements are false).
no idea how to do this HELP!
To determine which statement is false, we need to analyze the proposed mechanism and identify any inconsistencies.
Let's break down the mechanism step by step:
1. H2O2 + I- -> H2O + IO- (slow)
This is the slow step of the reaction, indicated by the "slow" label. It involves the direct reaction between hydrogen peroxide (H2O2) and iodide ion (I-) to form water (H2O) and iodate ion (IO-).
2. H2O2 + IO- -> H2O + O2 + I- (fast)
This is the fast step of the reaction, indicated by the "fast" label. It involves the reaction between hydrogen peroxide (H2O2) and iodate ion (IO-) to form water (H2O), oxygen gas (O2), and iodide ion (I-).
Now, let's examine each statement to see if they are consistent with the proposed mechanism:
a. The reaction is first order with respect to H2O2.
This statement is true. In the proposed mechanism, the first step involves the direct reaction between H2O2 and I-, without the involvement of any other reactant. Therefore, the rate of the reaction is only dependent on the concentration of H2O2, making it first order.
b. The reaction is first order with respect to I-.
This statement is false. In the proposed mechanism, the first step involves the consumption of one iodide ion (I-) to form iodate ion (IO-), but the overall rate of the reaction is not solely dependent on the concentration of I-. Therefore, the reaction is not first order with respect to I-.
c. I- is a catalyst.
This statement is false. A catalyst is a substance that speeds up a reaction without being consumed in the process. In the proposed mechanism, I- is consumed in the first step and then regenerated in the second step. It is not acting as a catalyst but rather as a reactant and an intermediate.
d. IO- is an intermediate.
This statement is true. An intermediate is a species that is formed and consumed during the reaction but does not appear in the overall balanced equation. In the proposed mechanism, IO- is formed in the first step and then consumed in the second step. It is an intermediate species.
Based on the analysis above, the false statement is b. The reaction is not first order with respect to I-. Therefore, the correct answer is (b).