JEE MAIN - Chemistry (2012 - No. 18)

For a first order reaction, (A) $$\to$$ products, the concentration of A changes from 0.1 M to 0.025 M in 40 minutes. The rate of reaction when the concentration of A is 0.01 M is :
1.73 x 10–5 M/ min
3.47 x 10–4 M/min
3.47 x 10–5 M/min
1.73 x 10–4 M/min

Explanation

For a first order reaction

$$k = {{2.0303} \over t}\,\log \,{a \over {a - x}}$$

$$ = {{2.303} \over {40}}\log {{0.1} \over {0.025}}$$

$$ = {{2.303} \over {40}}\log 4$$

$$ = {{2.303 \times 0.6020} \over {40}}$$

$$ = 3.47 \times {10^{ - 2}}$$

$$R = K{\left( A \right)^1} = 3.47 \times {10^{ - 2}} \times 0.01$$

$$ = 3.47 \times {10^{ - 4}}$$

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