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Chemistry · 2025 · 3 marks
CBSE 2025 · Region 6 · Set 1 · Q23
The rate of a reaction: A + B → product is given below as a function of different initial concentrations of A and B. Calculate the order of the…
The rate of a reaction: $\displaystyle \mathrm{A}+\mathrm{B} \longrightarrow$ product is given below as a function of different initial concentrations of A and B.
Calculate the order of the reaction with respect to A and B. Determine the rate constant of the reaction.
| Experiment | [A]$\displaystyle / \mathrm{mol} \mathrm{L}^{-1}$ | [B]/mol L $\displaystyle { }^{-1}$ | Initial Rate $\displaystyle / \mathrm{mol} \mathrm{L}^{-1} \mathrm{~min}^{-1}$ |
| $\displaystyle 1$ | $\displaystyle 0.01$ | $\displaystyle 0.01$ | $\displaystyle 5 \times 10^{-3}$ |
| $\displaystyle 2$ | $\displaystyle 0.02$ | $\displaystyle 0.01$ | $\displaystyle 1 \times 10^{-2}$ |
| $\displaystyle 3$ | $\displaystyle 0.01$ | $\displaystyle 0.02$ | $\displaystyle 5 \times 10^{-3}$ |
Marking-scheme solution
Rate = k [ A]p [B]q
$\displaystyle 5$·$\displaystyle 0$ × $\displaystyle 10$–$\displaystyle 3$= k [ $\displaystyle 0.01$]p [$\displaystyle 0.01$]q………Eq $\displaystyle 1$
$\displaystyle 1$·$\displaystyle 0$ × $\displaystyle 10$–$\displaystyle 2$= k [ $\displaystyle 0.02$]p [$\displaystyle 0.01$]q………Eq $\displaystyle 2$
$\displaystyle 5$·$\displaystyle 0$ × $\displaystyle 10$–$\displaystyle 3$= k [ $\displaystyle 0.01$]p [$\displaystyle 0.02$]q………Eq $\displaystyle 3$
On Comparing (eq1) and (eq3)
$\displaystyle 1$= ($\displaystyle 2$)q
q = $\displaystyle 0$
On Comparing (eq1) and (eq2)
(2)$\displaystyle 1$= ($\displaystyle 2$)p
p = $\displaystyle 1$
Order w·r·t A = $\displaystyle 1$
Order w·r·t B= $\displaystyle 0$
From eq $\displaystyle 1$
$\displaystyle 5$·$\displaystyle 0$ × $\displaystyle 10$–$\displaystyle 3$= k [ $\displaystyle 0.01$]$\displaystyle 1$ [$\displaystyle 0.01$]$\displaystyle 0$
k =$\displaystyle 0.5$ min–$\displaystyle 1$
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