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Chemistry · 2023 · 4 marks
CBSE 2023 · Region 1 · Set 1 · Q31
The rate of reaction is concerned with decrease in concentration of reactants or increase in the concentration of products per unit time. It can be…
The rate of reaction is concerned with decrease in concentration of reactants or increase in the concentration of products per unit time. It can be expressed as instantaneous rate at a particular instant of time and average rate over a large interval of time. Mathematical representation of rate of reaction is given by rate law. Rate constant and order of a reaction can be determined from rate law or its integrated rate equation.
(i)
What is average rate of reaction?
(ii)
Write two factors that affect the rate of reaction.
(iii)
(1)
What happens to rate of reaction for zero order reaction?
(2)
What is the unit of k for zero order reaction?
OR
(1)
For a reaction $\displaystyle \mathrm{P}+2 \mathrm{Q} \longrightarrow$ Products Rate $\displaystyle =\mathrm{k}[\mathrm{P}]^{1 / 2}[\mathrm{Q}]^{1}$. What is the order of the reaction?
(2)
Define pseudo first order reaction with an example.
Marking-scheme solution
(i)
Change in the concentration of a reactant or product per unit time.
(ii)
Concentration of reactants, Surface area, catalyst and temperature .
(iii)
(1)
rate is independent of the concentration of reactant(s) /rate remains constant / rate = k
(2)
\(\displaystyle \mathrm{mol} \mathrm{L}^{-1} \mathrm{~s}^{-1}\)
OR
(1)
$\displaystyle 3$/$\displaystyle 2$ / $\displaystyle 1.5$
(2)
A reaction that appears to be of higher order but follows first-order kinetics. Example: Hydrolysis of an ester
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CBSE Class 12 Chemistry past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.