Given below are two statements: one is labelled as Assertion and the other is labelled as Reason.

Assertion: At 10°C, the density of a 5 M solution of KCl [atomic masses of K & Cl are 39 & 35.5 g mol

Question

Given below are two statements: one is labelled as Assertion and the other is labelled as Reason.

Assertion: At 10°C, the density of a 5 M solution of KCl [atomic masses of K & Cl are 39 & 35.5 g mol⁻¹ respectively], is 'x' g mL⁻¹. The solution is cooled to −21°C. The molality of the solution will remain unchanged.

Reason: The molality of a solution does not change with temperature as mass remains unaffected with temperature.

In the light of the above statements, choose the correct answer from the options given below.

Canvas Classes · Accepted Answer

Strategy:
 Compare concentration terms based on their dependency on volume. Volume changes with temperature (expansion/contraction), but mass remains constant.

Step 1: Evaluate the Assertion
The assertion states that cooling a solution from 10°C to −21°C leaves the molality unchanged. Molality is defined as:

Since neither moles nor mass are affected by temperature, the molality indeed remains constant. Thus, the Assertion is True.

Step 2: Evaluate the Reason
The reason explains that molality

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