JEE Main · 2019 · Shift-IImediumCK-085

For an elementary chemical reaction, A2 k-1k1 2A, the expression for d[A]dt is:

Chemical Kinetics · Class 12 · JEE Main Previous Year Question

Question

For an elementary chemical reaction, $\mathrm{A_2} \underset{k_{-1}}{\stackrel{k_1}{\rightleftharpoons}} \mathrm{2A}$ , the expression for $\frac{d[\mathrm{A}]}{dt}$ is:

Options

a
$2k_1[\mathrm{A_2}] - 2k_{-1}[\mathrm{A}]^2$
✓
b
$2k_1[\mathrm{A_2}] - k_{-1}[\mathrm{A}]^2$
c
$k_1[\mathrm{A_2}] + k_{-1}[\mathrm{A}]^2$
d
$k_1[\mathrm{A_2}] - k_{-1}[\mathrm{A}]^2$

Correct Answera

$2k_1[\mathrm{A_2}] - 2k_{-1}[\mathrm{A}]^2$

Detailed Solution

For the forward reaction $\mathrm{A_2 \rightarrow 2A}$ : rate of formation of A $= 2k_1[\mathrm{A_2}]$

For the reverse reaction $\mathrm{2A \rightarrow A_2}$ : rate of consumption of A $= 2k_{-1}[\mathrm{A}]^2$

Net rate: $\frac{d[\mathrm{A}]}{dt} = 2k_1[\mathrm{A_2}] - 2k_{-1}[\mathrm{A}]^2$

Answer: Option (1)

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