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Chemistry · 2026 · 3 marks
CBSE 2026 · Region 3 · Set 2 · Q25
An antifreeze solution is prepared by dissolving 31 g of ethylene glycol (Molar mass =62 g mol^-1 ) in 600 g of water. Calculate the freezing point…
An antifreeze solution is prepared by dissolving $\displaystyle 31$ g of ethylene glycol (Molar mass $\displaystyle =62 \mathrm{~g} \mathrm{~mol}^{-1}$ ) in $\displaystyle 600$ g of water. Calculate the freezing point of the solution. $\displaystyle \left(\mathrm{K}_{\mathrm{f}}\right.$ for water $\displaystyle \left.=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right)$
Marking-scheme solution
\[\begin{array}{l}
\Delta T_f = K_f \cdot \dfrac{W_B}{M_B} \times \dfrac{1000}{W_A} \\
\Delta T_f = 1.86 \times \dfrac{31}{62} \times \dfrac{1000}{600} \\
\Delta T_f = 1.55\ \mathrm{K} \\
T_f^{0} = T_f - 1.55\ \mathrm{K} \\
T_f = 0^{\circ}\mathrm{C} - 1.55^{\circ}\mathrm{C} \\
T_f = -1.55^{\circ}\mathrm{C} \quad \text{OR} \\
T_f = 273.15 - 1.55 = 271.6\ \mathrm{K}
\end{array}
\]
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CBSE Class 12 Chemistry past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.