The rate of decomposition of N₂O₅ in CCl₄ solution has been studied at 318 K and the following results have been obtained:

t (in mitt)

0

135

339

683

1680

C (mol L^–1)

2.08

1.91

1.68

1.35

0.57

Find the order of reaction and calculate its rate constant.

Solution

It can be seen that the rate of reaction does not remain constant with time and, therefore it is not a zero order reaction.

(i) at t = 135 \min; k = \frac{2.303}{135 \min} \log \frac{2.08}{191} = 6.32 \times 10^{- 4} \min^{- 1} (ii) at t = 339 \min; k = \frac{2.303}{339 \min} \log \frac{2.08}{1.68} = 6.30 \times 10^{- 4} \min^{- 1} (iii) at t = 683 \min; k = \frac{2.303}{683 \min} \log \frac{2.08}{1.35} = 6.32 \times 10^{- 4} \min^{- 1} (iv) at t = 1680 \min; k = \frac{2.303}{1680 \min} \log \frac{2.08}{0.57} = 6.31 \times 10^{-^{4}} \min^{- 1}

It is observed that the value of k is almost constant for all experimental results and hence it is first order reaction with k = 6.31 x 10^–4 min^–1.

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