JEE Main 2018 — Chemistry Physical Chemistry

2018mcqmedium

At 320 K, a gas ${A}_{2}$ is 20 % dissociated to $A(g)$ . The standard Gibbs free energy change at $320 K and 1 atm in J mo{l}^{–1}$ is approximately: $(R = 8.314 {\mathrm{JK}}^{–1} {\mathrm{mol}}^{–1} ;\mathrm{ln}2 = 0.693 ;\mathrm{ln}3 = 1.098)$

Official previous-year question

Held on 16 Apr 2018 · Verified 6 Jul 2026.

Options

A
1844
B
2068
C
4281
D
4763

Did you get this right?

Solution

Let assume initial moles is 1

${ A}_{2}\overset{ }{\rightarrow } 2A$

t=0 1

t=t $1-0.2 0.2\times 2$

$Partial pressure of {A}_{2}=\frac{0.8}{1.2}\times 1$

$Partial pressure of A=\frac{0.4}{1.2}\times 1$

${k}_{p}=\frac{{(\frac{0.4}{1.2})}^{2}\times 1}{(\frac{0.8}{1.2})\times 1 }=\frac{1}{6}$

$\Delta G^{\circ}= -RTlnk=-8.314\times 320 ln\frac{1}{6}$

$=8.314\times 320 (0.693+1.098)$

$⋍4763 J/mole$

Your note

JEE Main Physical Chemistry in other years

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

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JEE Main 2018 — Chemistry Physical Chemistry

2018mcqmedium

Official previous-year question

Held on 16 Apr 2018 · Verified 6 Jul 2026.

Options

A
1844
B
2068
C
4281
D
4763

Did you get this right?

Solution

Let assume initial moles is 1

${ A}_{2}\overset{ }{\rightarrow } 2A$

t=0 1

t=t $1-0.2 0.2\times 2$

$Partial pressure of {A}_{2}=\frac{0.8}{1.2}\times 1$

$Partial pressure of A=\frac{0.4}{1.2}\times 1$

${k}_{p}=\frac{{(\frac{0.4}{1.2})}^{2}\times 1}{(\frac{0.8}{1.2})\times 1 }=\frac{1}{6}$

$\Delta G^{\circ}= -RTlnk=-8.314\times 320 ln\frac{1}{6}$

$=8.314\times 320 (0.693+1.098)$

$⋍4763 J/mole$

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 2018 — Chemistry Physical Chemistry

Options

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

JEE Main 2018 — Chemistry Physical Chemistry

Options

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