JEE Main 2019 — Chemistry Physical Chemistry

2019mcqmedium

The process with negative entropy change is:

Official previous-year question

Held on 10 Jan 2019 · Verified 6 Jul 2026.

Options

A
Synthesis of ammonia from ${N}_{2}$ and ${H}_{2}$ .
B
Dissolution of iodine in water.
C
Dissociation of ${\mathrm{CaSO}}_{4}(s)$ to $\mathrm{CaO}(s)$ and ${\mathrm{SO}}_{3}(g)$ .
D
Sublimation of dry ice.

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Solution

If a process leads to the arrangement in a system, it will have a negative entropy, whereas if disorder increases, the entropy will be positive. When the number of moles of a gas increases, or ice melts, the disorder increases. Freezing of water, crystallization, combination reactions etc, leads to an arrangement.

${\mathrm{CO}}_{2}(s)\rightarrow {\mathrm{CO}}_{2}(g);\Delta S=+\mathrm{ve}(\Delta {n}_{g}>0)$

${N}_{2}(g)+3{H}_{2}(g)\rightarrow 2{\mathrm{NH}}_{3}(g);\Delta S=-\mathrm{ve}(\Delta {n}_{g}=-\mathrm{ve})$

${\mathrm{CaCO}}_{3}(s)\rightarrow \mathrm{CaO}(s)+{\mathrm{CO}}_{2}(g);\Delta S=+\mathrm{ve}(\Delta {n}_{g}>0)$

Dissolution of ${\text{I}}_{2}$ in ${H}_{2}O;\Delta S=+\mathrm{ve}$ .

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JEE Main Physical Chemistry in other years

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JEE Main 2019 — Chemistry Physical Chemistry

2019mcqmedium

The process with negative entropy change is:

Official previous-year question

Held on 10 Jan 2019 · Verified 6 Jul 2026.

Options

A
Synthesis of ammonia from ${N}_{2}$ and ${H}_{2}$ .
B
Dissolution of iodine in water.
C
Dissociation of ${\mathrm{CaSO}}_{4}(s)$ to $\mathrm{CaO}(s)$ and ${\mathrm{SO}}_{3}(g)$ .
D
Sublimation of dry ice.

Did you get this right?

Solution

${\mathrm{CO}}_{2}(s)\rightarrow {\mathrm{CO}}_{2}(g);\Delta S=+\mathrm{ve}(\Delta {n}_{g}>0)$

${N}_{2}(g)+3{H}_{2}(g)\rightarrow 2{\mathrm{NH}}_{3}(g);\Delta S=-\mathrm{ve}(\Delta {n}_{g}=-\mathrm{ve})$

${\mathrm{CaCO}}_{3}(s)\rightarrow \mathrm{CaO}(s)+{\mathrm{CO}}_{2}(g);\Delta S=+\mathrm{ve}(\Delta {n}_{g}>0)$

Dissolution of ${\text{I}}_{2}$ in ${H}_{2}O;\Delta S=+\mathrm{ve}$ .

Your note

JEE Main Physical Chemistry in other years

Keep practicing Physical Chemistry

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

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JEE Main 2019 — Chemistry Physical Chemistry

Options

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Solution

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JEE Main Physical Chemistry in other years

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Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

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JEE Main 2019 — 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