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Solutions question

2011 · Q66
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Solutions question

2011 · Q66

NEETChemistrySolutionsMCQ+4 / −1
A 0.1 molal aqueous solution of a weak acid is 30% ionized. If Kf for water is 1.86oC/m, the freezing point of the solution will be
  1. A
    −-−0.18oC
  2. B
    −-−0.54oC
  3. C
    −-−0.36oC
  4. D
    −-−0.24oC
View written solutionFree

Correct answer: D

We know that Δ\Delta ΔTf = i × Kf × m

Here i is van’t Hoff’s factor.

i for weak acid is 1 + α\alpha α.

Here α\alpha α is degree of dissociation i.e., 30/100 = 0.3

∴\therefore∴ i = 1 + α\alpha α = 1 + 0.3 = 1.3

∴\therefore∴ Tf = i × Kf × m = 1.3 × 1.86 × 0.1 = 0.24

∴\therefore∴ Freezing point = – 0.24

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