CBSE 2026 · Region 5 · Set 1 · Q17 · 2 marks
1.$\displaystyle 00$ molal aqueous solution of trichloroacetic acid is heated to its boiling point. Boiling point of this solution was found to be $\displaystyle 100 \cdot 18^{\circ} \mathrm{C}$. Calculate the van't Hoff factor for trichloroacetic acid. (Given : $\displaystyle \mathrm{K}_{\mathrm{b}}$ for water $\displaystyle =0.512 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$) State Henry's law. Calculate the mole fraction of $\displaystyle \mathrm{CO}_{2}$ in water at $\displaystyle 298$ K under $\displaystyle 760$ mm Hg. (Given : $\displaystyle \mathrm{K}_{\mathrm{H}}$ for $\displaystyle \mathrm{CO}_{2}$ in $\displaystyle \mathrm{H}_{2} \mathrm{O}$ at $\displaystyle 298 \mathrm{~K}=1 \cdot 25 \times 10^{6} \mathrm{~mm} \mathrm{Hg}$ )
1.$\displaystyle 00$ molal aqueous solution of trichloroacetic acid is heated to its boiling point. Boiling point of this solution was found to be $\displaystyle 100 \cdot 18^{\circ} \mathrm{C}$. Calculate the van't Hoff factor for trichloroacetic acid. (Given : $\displaystyle \mathrm{K}_{\mathrm{b}}$ for water $\displaystyle =0.512 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$)
State Henry's law. Calculate the mole fraction of $\displaystyle \mathrm{CO}_{2}$ in water at $\displaystyle 298$ K under $\displaystyle 760$ mm Hg. (Given : $\displaystyle \mathrm{K}_{\mathrm{H}}$ for $\displaystyle \mathrm{CO}_{2}$ in $\displaystyle \mathrm{H}_{2} \mathrm{O}$ at $\displaystyle 298 \mathrm{~K}=1 \cdot 25 \times 10^{6} \mathrm{~mm} \mathrm{Hg}$ )
Marking-scheme solution
∆Tb = Kb × m
∆Tb = $\displaystyle 1$ × $\displaystyle 0.512$
= $\displaystyle 0.512$
Van’t Hoff factor (i) = Observed colligative property
Calculated colligative property
=
= $\displaystyle 0.3516$
Alternative method
ΔTb = i Kb m
(Tb - Tb°) = i x $\displaystyle 0.512$ x $\displaystyle 1$
0.$\displaystyle 18$ = $\displaystyle 0.512$ x i
i =
i = $\displaystyle 0.3516$
At a given temperature, the solubility of a gas in a liquid is directly proportional
to the partial pressure of the gas.
p = KH xCO2
xCO2 =
1.$\displaystyle 25$ 𝑋 $\displaystyle 106$
= $\displaystyle 6.08$ x $\displaystyle 10$−$\displaystyle 4$
SolutionsColligative Properties and Determination of Molar MassApplyvery_short_answermedium
More from Solutions
- 0.3 g of acetic acid (M=60 g mol^-1) dissolved in 30 g of benzene shows a depression in freezing point equal…2023 · asked 6×
- Define molal depression constant. How is it related to enthalpy of fusion? OR What type of deviation is shown…2024 · asked 3×
- When a liquid and its vapour are at equilibrium and the pressure is suddenly decreased:2026 · asked 3×
- Shweta mixed two liquids A and B of 10 mL each. After mixing, the volume of the solution was found to be 20 ·…2025 · asked 3×
- Explain the following with the help of Henry's law: (i) Bends (ii) Anoxia OR How does sprinkling of salt help…2026 · asked 3×
- Calculate the vapour pressure of a solution containing 61 g of benzoic acid (molar mass =122 g mol^-1 )…2026 · asked 3×
- The boiling point of one molal NaCl solution, assuming NaCl to be completely dissociated in water is: (K b.…2026 · asked 3×
- Give reasons: Cooking is faster in pressure cooker than in an open pan. On mixing liquid X and liquid Y,…2025 · asked 3×
CBSE Class 12 Chemistry past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.