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Chemistry · 2026 · 3 marks
CBSE 2026 · Region 5 · Set 1 · Q23
(a) Define order of a reaction. (b) The rate for the following reaction is given by: A + B → C Rate = k [ A ][ B ]^2 (i) How is the rate of reaction…
(a)
Define order of a reaction.
(b)
The rate for the following reaction is given by : $\displaystyle \mathrm{A}+\mathrm{B} \rightarrow \mathrm{C}$ Rate $\displaystyle =\mathrm{k}[\mathrm{A}][\mathrm{B}]^{2}$
(i)
How is the rate of reaction affected if we double the concentration of B ?
(ii)
Write the overall order of a reaction if 'A' is present in large excess. []
Marking-scheme solution
(a)
The sum of powers of concentration of the reactants in the rate law expression is
called order of the reaction.
(b)(i)
Rate becomes $\displaystyle 4$ times.
(ii)
Order is $\displaystyle 2$
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CBSE Class 12 Chemistry past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.