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NCERT Class XII Chemistry
Chapter - Chemical Kinetics
Questions with Solutions

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Question : 6 of 39
Marks: +1, -0
A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is
(i) doubled
(ii) reduced to half ?
Solution:  
Rate =kR2= kR^{2}
(i) If [A]=2R,[A]=2 R, rate =k(2R)2=4kR2=k(2 R)^{2}=4 k R^{2} i.e. rate of reaction increases 4 timeswhen concentration is doubled.
(ii) If [A]=12R,[A]=\frac{1}{2} R, rate =k(R2)2=14kR2    =k\left(\frac{R}{2}\right)^{2}=\frac{1}{4} k R^{2} \;\; i.e. rate becomes 14th\frac{1}{4} \text{th} whenconcentration is reduced to 12\frac{1}{2}
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