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Chemical Kinetics — Chemistry STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceChemistryChemical Kinetics3 Marks
Question
A reaction is first order in A and second order in B.
(i) Write the differential rate equation.
(ii) How is the rate affected on increasing the concentration of B three times?
(iii) How is the rate affected when the concentration of both A and B are doubled?
✓

Answer

The reaction is of first order towards A and second order towards B hence :
(i) Differential rate equation : Rate $= k [ A ]^1[B]^2$
Hence, order of total reaction = 1 + 2 = 3
(ii) On tripling the concentration of B :
$\begin{array}{l}\text { Rate }= k [ A ]^1[3 B]^2 \\ \text { Rate }=9 k [ A ]^1[B]^2\end{array}$
Hence, rate of reaction becomes 9 times.
(iii) On doubling the concentration of both A and B :
$\begin{array}{l}\text { Rate }= k [ A ]^1[B]^2 \\ \text { Rate }= k [2 A]^1[2 B]^2 \\ \text { Rate }=8 k [ A ]^1[B]^2\end{array}$
Hence, rate of reaction becomes 8 times.

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