Question
A solution of $\ce{H_2O_2}$ when titrated against $\ce{KMnO_4}$ solution at different intervals of time gave the following results:
Time $($minutes$)$ $0$ $10$ $20$
Volume of $\ce{KMnO_4 (mL)}$ $23.8$ $14.7$ $9.1$
Show that decomposition of $\ce{H_2O_2}$​​​​​​​ is first order reaction.

Answer

  1. $\text{k}=\frac{2.303}{14.7}\log\frac{2.303}{10}=\frac{2.303}{10}\times0.2093=0.048\min^{-1}$
  2. $\text{k}=\frac{2.303}{20}\log\frac{2.303}{9.1}=\frac{2.303}{20}\times0.4176=0.048\min^{-1}$
Since the value of $k$ comes out to be constant in both the cases.
therefore the reaction is of first order.

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