Question

Consider the following reaction
$A + B \rightarrow C$
The time taken for A to become 1/4th of its initial concentration is twice the time taken to become 1/2 of the same. Also, when the change of concentration of B is plotted against time, the resulting graph gives a straight line with a negative slope and a positive intercept on the concentration axis.
The overall order of the reaction is ____.

Answer 1

Order with respect to A
For a first-order reaction:
$t_{75\%} = 2 \times t_{50\%}.$
This is consistent with the information given, so the reaction is first order with respect to A.
Order with respect to B The plot of [B] versus $t$ is a straight line, which indicates that the reaction is zero order with respect to B.
Overall order of the reaction:
$\text{Order} = 1 \, (\text{w.r.t. A}) + 0 \, (\text{w.r.t. B}) = 1.$
Final Answer:$1.$

Answer 2

Order with respect to A
For a first-order reaction:
$t_{75\%} = 2 \times t_{50\%}.$
This is consistent with the information given, so the reaction is first order with respect to A.
Order with respect to B The plot of [B] versus $t$ is a straight line, which indicates that the reaction is zero order with respect to B.
Overall order of the reaction:
$\text{Order} = 1 \, (\text{w.r.t. A}) + 0 \, (\text{w.r.t. B}) = 1.$
Final Answer:$1.$