Question

$75\%$ of a first order reaction is completed in $32$ minutes. $50\%$ of the reaction will be completed in:

• A. $24$ mins
• B. $16$ mins
• C. $18$ mins
• D. $23$ mins

Answer 1

The correct option is B $16$ mins

For a first-order reaction, we have:

$t_{75\%}=2t_{50\%}$

Given: $t_{75\%}=32$ min

Substituting the values in the above expression, we get-

$32$ min $=2t_{50\%}$

$t_{50\%}=16$ mins

Hence, $50\%$ of the reaction would have been completed in $16$ mins.