'x' g of NaCl is added to water in a beaker with a lid. The temperature of the system is raised from 1°C to 25°C.

Question

'x' g of NaCl is added to water in a beaker with a lid. The temperature of the system is raised from \(1^\circ C\) to \(25^\circ C\). Which out of the following plots, is best suited for the change in the molarity (M) of the solution with respect to temperature ?

[Consider the solubility of NaCl remains unchanged over the temperature range]

(1) 

(2) 

(3) 

(4) 

Answer 1

Correct option is: (2) 

\(\underset{1^\circ C}{\text{Water}} \xrightarrow[\text{decreases}]{\text{Volume}} \underset{4^\circ C }{\text{Water}} \xrightarrow[\text{thermal expansion}]{\text{Volume increases}} \underset{25^\circ C}{\text{Water}}\)

\(\text{Molarity} = \frac{n_\text{solute}}{\text{(Volume of solution)}_\ell}\)

Hence

\(1^\circ C \xrightarrow[\text{increases}]{\text{molarity}} 4^\circ C \xrightarrow[\text{decreases}]{\text{molarity}} 25^\circ C\)