Question

Consider the following reaction in an aqueous solution \[ \mathrm{I}^-(aq) + \mathrm{OCl}^- \rightarrow \mathrm{IO}^-(aq) + \mathrm{Cl}^-(aq) \] and the following initial concentration and initial rate data for this reaction.

Which of the following is the correct rate law for this reaction?

• A. Rate \(= k [\mathrm{I}^-]^2[\mathrm{OCl}^-]\)
• B. Rate \(= k[\mathrm{OCl}^-]\)
• C. Rate \(= k [\mathrm{I}^-]^2\)
• D. Rate \(= k[\mathrm{I}^-][\mathrm{OCl}^-]\)

Hint:

Compare experiments where only one reactant concentration changes.

Answer 1

The Correct Option is D

Step 1: Formula / Definition}
\[ \text{Rate} = k[\mathrm{I}^-]^x[\mathrm{OCl}^-]^y \]
Step 2: Calculation / Simplification}
Exp 1 & 2: \([\mathrm{OCl}^-]\) constant, \([\mathrm{I}^-]\) doubles \(\Rightarrow\) rate doubles \(\Rightarrow x = 1\)
Exp 3 & 4: \([\mathrm{I}^-]\) constant, \([\mathrm{OCl}^-]\) doubles \(\Rightarrow\) rate doubles \(\Rightarrow y = 1\)
\(\text{Rate} = k[\mathrm{I}^-][\mathrm{OCl}^-]\)
Step 3: Final Answer
\[ \text{Rate} = k[\mathrm{I}^-][\mathrm{OCl}^-] \]