JEE Main 2023 — Chemistry Physical Chemistry

2023integermedium

The reaction $2\mathrm{NO}+{\mathrm{Br}}_{2}\rightarrow 2\mathrm{NOBr}$ takes place through the mechanism given below

$\mathrm{NO}+{\mathrm{Br}}_{2}\overset{}{\rightleftharpoons }{\mathrm{NOBr}}_{2}(\mathrm{fast})$

${\mathrm{NOBr}}_{2}+\mathrm{NO}\rightarrow 2\mathrm{NOBr}(\mathrm{slow})$

The overall order of the reaction is _____.

Official previous-year question

Held on 12 Apr 2023 · Verified 6 Jul 2026.

Did you get this right?

Solution

On applying Law of mass action over slowest step,

$R=k[{\mathrm{NOBr}}_{2}][\mathrm{NO}]$

The slowest step is the rate determining step.

On applying Law of mass action on equilibrium of Step I

$k=\frac{[{\mathrm{NOBr}}_{2}]}{[\mathrm{NO}][{\mathrm{Br}}_{2}]}$

$[{\mathrm{NOBr}}_{2}]=k[\mathrm{NO}][{\mathrm{Br}}_{2}]$

Hence, overall rate equation will be

$R=k{[\mathrm{NO}]}^{2}[{\mathrm{Br}}_{2}]$

$=k'{[\mathrm{NO}]}^{2}[{\mathrm{Br}}_{2}]$

The overall order is equal to sum of the powers of the concentration terms in the rate law.

The overall order of the reaction is 3.

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JEE Main Physical Chemistry in other years

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JEE Main 2023 — Chemistry Physical Chemistry

2023integermedium

The reaction $2\mathrm{NO}+{\mathrm{Br}}_{2}\rightarrow 2\mathrm{NOBr}$ takes place through the mechanism given below

$\mathrm{NO}+{\mathrm{Br}}_{2}\overset{}{\rightleftharpoons }{\mathrm{NOBr}}_{2}(\mathrm{fast})$

${\mathrm{NOBr}}_{2}+\mathrm{NO}\rightarrow 2\mathrm{NOBr}(\mathrm{slow})$

The overall order of the reaction is _____.

Official previous-year question

Held on 12 Apr 2023 · Verified 6 Jul 2026.

Did you get this right?

Solution

On applying Law of mass action over slowest step,

$R=k[{\mathrm{NOBr}}_{2}][\mathrm{NO}]$

The slowest step is the rate determining step.

On applying Law of mass action on equilibrium of Step I

$k=\frac{[{\mathrm{NOBr}}_{2}]}{[\mathrm{NO}][{\mathrm{Br}}_{2}]}$

$[{\mathrm{NOBr}}_{2}]=k[\mathrm{NO}][{\mathrm{Br}}_{2}]$

Hence, overall rate equation will be

$R=k{[\mathrm{NO}]}^{2}[{\mathrm{Br}}_{2}]$

$=k'{[\mathrm{NO}]}^{2}[{\mathrm{Br}}_{2}]$

The overall order is equal to sum of the powers of the concentration terms in the rate law.

The overall order of the reaction is 3.

Your note

JEE Main Physical Chemistry in other years

Keep practicing Physical Chemistry

Work through every JEE Main Physical Chemistry PYQ, year by year.

Browse all Chemistry topics

JEE Main 2023 — Chemistry Physical Chemistry

Did you get this right?

Solution

Your note

JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

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JEE Main 2023 — Chemistry Physical Chemistry

Did you get this right?

Solution

Your note

JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry