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Chemistry · 2025 · 3 marks
CBSE 2025 · Region 4 · Set 1 · Q25
An aqueous solution of NaOH was made and its molar mass from the measurement of osmotic pressure at 27^° C was found to be 25 g mol^-1. Calculate the…
An aqueous solution of NaOH was made and its molar mass from the measurement of osmotic pressure at $\displaystyle 27^{\circ} \mathrm{C}$ was found to be $\displaystyle 25 \mathrm{~g} \mathrm{~mol}^{-1}$. Calculate the percentage dissociation of NaOH in this solution. [Atomic mass : $\displaystyle \mathrm{Na}=23 \mathrm{u}, \mathrm{O}=16 \mathrm{u}, \mathrm{H}=1 \mathrm{u}$ ]
Marking-scheme solution
i=Normal molar mass/Abnormal molar mass
i=$\displaystyle 40$/$\displaystyle 25$
α= i-$\displaystyle 1$/n-$\displaystyle 1$
=$\displaystyle 60$%
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CBSE Class 12 Chemistry past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.