Test Index

MHTCET 23 Apr 2025 Shift 1 Paper

Question : 54 of 150

Marks: +1, -0

Which from following reactions is exothermic?

$\mathrm{KOH}_{(\mathrm{aq})}+\mathrm{HNO}_{3(\mathrm{aq})} \longrightarrow \mathrm{KNO}_{3(\mathrm{aq})}+\mathrm{H}_{2} \mathrm{O}$
$\mathrm{H}_{2} \mathrm{O}_{(\mathrm{s})} \longrightarrow \mathrm{H}_{2} \mathrm{O}_{(l)}$
$\mathrm{NaCl}_{(\mathrm{s})}+\mathrm{aq} \longrightarrow \mathrm{Na}_{(\mathrm{aq})}^{+}+\mathrm{Cl}_{(\mathrm{aq})}^{-}$
$\mathrm{N}_{2(\mathrm{~g})}+2 \mathrm{O}_{2(\mathrm{~g})} \longrightarrow 2 \mathrm{NO}_{2(\mathrm{~g})}$

Solution:

Concept:

Neutralisation of a strong acid and a strong base releases heat energy, so it is exothermic.

Explanation:

Option A:

\mathrm{KOH}_{(\mathrm{aq})}+\mathrm{HNO}_{3(\mathrm{aq})} \longrightarrow \mathrm{KNO}_{3(\mathrm{aq})}+\mathrm{H}_{2} \mathrm{O}

is an acid–base neutralisation reaction.

Neutralisation reactions always release heat.

Hence, this reaction is exothermic.

Other options are endothermic: melting of ice (B), dissolution of

\mathrm{NaCl}

(C), and formation of

\mathrm{NO}_{2}

from

\mathrm{N}_{2}

and

\mathrm{O}_{2}

(D).

Answer:

Option A

Go to Question:

Prev Question

Next Question