MHT CET · Chemistry · Solutions

What mass of solute (molar mass \(58 \mathrm{~g} \mathrm{~mol}^{-1}\) ) is to be dissolved in \(2.5 \mathrm{dm}^3 \mathrm{H}_2 \mathrm{O}\) to generate osmotic pressure of 0.245 atm at 300 K ? \(\left(\mathrm{R}=0.0821 \mathrm{dm}^3 \mathrm{~atm} \mathrm{~K} \mathrm{~mol}^{-1}\right)\).

A 1.0 gram
B 0.72 gram
C 1.44 gram
D 1.75 gram

Verified Solution

Answer & Solution

Correct Answer

(C) 1.44 gram

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & \Pi=C R T \\ & \Pi=\frac{\mathrm{W}_2 \times \mathrm{R} \times \mathrm{T}}{\mathrm{M}_2 \times \mathrm{V}} \\ & \mathrm{W}_2=\frac{\Pi \times \mathrm{M}_2 \times \mathrm{V}}{\mathrm{R} \times \mathrm{T}} \\ & \quad \mathrm{W}_2=\frac{0.245 \mathrm{~atm} \times 58 \mathrm{~g} \mathrm{~mol}^{-1} \times 2.5 \mathrm{dm}^3}{0.0821 \mathrm{dm}^3 \mathrm{~atm} \mathrm{~K}^{-1} \mathrm{~mol}^{-1} \times 300 \mathrm{~K}} \\ & \therefore \quad \text { Mass of solute }=1.44 \mathrm{~g}\end{aligned}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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