Question

Equal volumes of methanoic acid and sodium hydroxide are mixed, if x is the heat of formation of water, then heat evolved on neutralisation is

(a) twice of x
(b) equal to x
(c) more than x
(d) less than x

Answer 1

Explanation:

Methanoic acid is a weak acid and therefore, energy will be required for its dissociation. Thus, the energy released on neutralisation of methanoic acid and sodium hydroxide giving salt and water will be less than the heat evolved during the formation of water.

Hence, the heat evolved on neutralisation will be less than x.

Answer 2

QUESTION

• Equal volumes of methanoic acid and sodium hydroxide are mixed, if x is the heat of formation of water, then heat evolved on neutralisation is

OPTIONS

• (a) twice of x
• (b) equal to x
• (c) more than x
• (D) less than x

Correct Answer

• less than x

EXPLANATION

“Methanoic acid(HCOOH), Sodium hydroxide(NaOH). Weak acid and strong base neutralisation.

H⁺ + OH⁻ → H₂O + x(Heat of formation),

HCOOH ⇌ HCOO⁻ + H⁺, NaOH ⇌ Na⁺ + OH⁻,

H⁺ + OH⁻ ⇌ H₂O + Less than x (Heat of reaction).

Because, some of the energy is lost in ionization of weak acid, HCOOH.”.