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JEE Advanced Chemistry Solutions 2021 JEE Advanced 2021 (Paper 1)

JEE Advanced Chemistry Question (2021) — Solution

Question

The boiling point of water in a 0.1 molal silver nitrate solution (solution A ) is x ^ C . To this solution A , an equal volume of 0.1 molal aqueous barium chloride solution is added to make a new solution B. The difference in the boiling points of water in the two solutions A and B is y 10^ -2 ^ C . (Assume: Densities of the solutions A and B are the same as that of water and the soluble salts dissociate completely. Use: Molal elevation constant (Ebullioscopic Constant), K_ b =0.5 ~K ~kg ~mol ^ -1 ; Boiling point of pure water as 100^ C .) The value of  y is ___.

Options

  1. A. A
  2. B. B
  3. C. C
  4. D. D

Answer

A. A

Step-by-step solution

After adding  BaCl 2  solution in  AgNO 3 solution  AgCl  will be precipitate. Since volume of both solutions are equal let's take V = 1   L  of each. so initial moles of  AgNO 3 = 0 .1   mole initial moles of  BaCl 2 = 0 .1   mole 2   AgNO 3 + BaCl 2 → 2 AgCl ↓ + Ba NO 3 2 2 AgNO 3 + BaCl 2 → 2 AgCl ↓ + Ba NO 3 2 Intial   moles 0 .1 0 .1 Change 0 .1 − 0 .05 + 0 .1 + 0 .05 Final   moles 0 0 .05 0 .05 Final   concentration 0 .05 2 0 .05 2 New  ΔT b = 1   K b   m 3 × 0 .05 2 + 3 × 0 .05 2 × 0 .5 = 0 .075 ∘ C Difference in boiling point of both solution = ΔT b 1 − ΔT b 2 = 0 .1 − 0 .075 = 0 .025 = 2 .5 × 10 − 2 K

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