NEET UG 2019 — Chemistry Physical Chemistry

2019mcqeasy

For the chemical reaction ${N}_{2}(g)+3{H}_{2}(g)\rightleftharpoons 2N{H}_{3}(g)$ , the correct option is:

Official previous-year question

Held on 30 Apr 2019 · Verified 9 Jul 2026.

Options

A
$-\frac{1}{3}\frac{d[{H}_{2}]}{dt}=-\frac{1}{2}\frac{d[N{H}_{3}]}{dt}$
B
$-\frac{d[{N}_{2}]}{dt}=2\frac{d[N{H}_{3}]}{dt}$
C
$-\frac{d[{N}_{2}]}{dt}=\frac{1}{2}\frac{d[N{H}_{3}]}{dt}$
D
$3\frac{d[{H}_{2}]}{dt}=2\frac{d[N{H}_{3}]}{dt}$

Did you get this right?

Solution

For the reaction ${N}_{2}(g)+3{H}_{2}(g)\rightleftharpoons 2N{H}_{3}(g)$ ,

Rate= $\frac{\mathrm{Change}\mathrm{in}\mathrm{concentration}\mathrm{of}\mathrm{reactants}\mathrm{or}\mathrm{products}}{\mathrm{time}\mathrm{taken}\mathrm{for}\mathrm{change}}$

Rate $=\frac{-d[{N}_{2}]}{dt}=\frac{-1}{3}\frac{d[{H}_{2}]}{dt}=\frac{1}{2}\frac{d[N{H}_{3}]}{dt}$

$\therefore \frac{-d[{N}_{2}]}{dt}=\frac{1}{2}\frac{d[N{H}_{3}]}{dt}$

A negative sign before a reaction rate symbol signifies a decrease in concentration of reactant with increase of time.

Your note

NEET UG Physical Chemistry in other years

Physical Chemistry 2026 Physical Chemistry 2025 Physical Chemistry 2024 Physical Chemistry 2023 Physical Chemistry 2022 Physical Chemistry 2021 Physical Chemistry 2020 Physical Chemistry 2018 Physical Chemistry 2017 Physical Chemistry 2016 Physical Chemistry 2015 Physical Chemistry 2014

More NEET UG Physical Chemistry questions

For the reaction 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), ΔH = -198 kJ. Which condition favours forward reaction?

2026medium

The unit of rate constant for a first-order reaction is:

2026easy

The conjugate base of H₂SO₄ is:

2025easy

Phosphoric acid ionizes in three steps with their ionization constant values $\mathrm{K}_{\mathrm{a}_1}, \mathrm{~K}_{\mathrm{a}_2}$ and $\mathrm{K}_{\mathrm{a}_3}$, respectively, While K is the overall ionization constant. Which of the following statements are true? A. $\log \mathrm{K}=\log \mathrm{K}_{\mathrm{a}_1}+\log \mathrm{K}_{\mathrm{a}_2}+\log \mathrm{K}_{\mathrm{a}_3}$ B. $\mathrm{H}_3 \mathrm{PO}_4$ is a stronger acid than $\mathrm{H}_2 \mathrm{PO}_4^{-}$and $\mathrm{HPO}_4^{2-}$ C. $K_{a_1}\gt K_{a_2}\gt K_{a_3}$ D. $\mathrm{K}_{\mathrm{a}_1}=\frac{\mathrm{K}_{\mathrm{a}_3}+\mathrm{K}_{\mathrm{a}_2}}{2}$ Choose the correct answer from the options given below:

2025medium

If the half-life $\left(\mathrm{t}_{1 / 2}\right)$ for a first order reaction is 1 minutes, then the time required for $99.9 \%$ completion of the reaction is closest to:

2025medium

View all Physical Chemistry questions

Keep practicing Physical Chemistry

Work through every NEET UG Physical Chemistry PYQ, year by year.

Browse all Chemistry topics

NEET UG 2019 — Chemistry Physical Chemistry

2019mcqeasy

For the chemical reaction ${N}_{2}(g)+3{H}_{2}(g)\rightleftharpoons 2N{H}_{3}(g)$ , the correct option is:

Official previous-year question

Held on 30 Apr 2019 · Verified 9 Jul 2026.

Options

A
$-\frac{1}{3}\frac{d[{H}_{2}]}{dt}=-\frac{1}{2}\frac{d[N{H}_{3}]}{dt}$
B
$-\frac{d[{N}_{2}]}{dt}=2\frac{d[N{H}_{3}]}{dt}$
C
$-\frac{d[{N}_{2}]}{dt}=\frac{1}{2}\frac{d[N{H}_{3}]}{dt}$
D
$3\frac{d[{H}_{2}]}{dt}=2\frac{d[N{H}_{3}]}{dt}$

Did you get this right?

Solution

For the reaction ${N}_{2}(g)+3{H}_{2}(g)\rightleftharpoons 2N{H}_{3}(g)$ ,

Rate= $\frac{\mathrm{Change}\mathrm{in}\mathrm{concentration}\mathrm{of}\mathrm{reactants}\mathrm{or}\mathrm{products}}{\mathrm{time}\mathrm{taken}\mathrm{for}\mathrm{change}}$

Rate $=\frac{-d[{N}_{2}]}{dt}=\frac{-1}{3}\frac{d[{H}_{2}]}{dt}=\frac{1}{2}\frac{d[N{H}_{3}]}{dt}$

$\therefore \frac{-d[{N}_{2}]}{dt}=\frac{1}{2}\frac{d[N{H}_{3}]}{dt}$

A negative sign before a reaction rate symbol signifies a decrease in concentration of reactant with increase of time.

NEET UG 2019 — Chemistry Physical Chemistry

Options

Did you get this right?

Solution

Your note

NEET UG Physical Chemistry in other years

More NEET UG Physical Chemistry questions

Other Chemistry topics for NEET UG

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry

NEET UG 2019 — Chemistry Physical Chemistry

Options

Did you get this right?

Solution

Your note

NEET UG Physical Chemistry in other years

More NEET UG Physical Chemistry questions

Other Chemistry topics for NEET UG

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry