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AP EAMCET2008ChemistrySolutions

When 25 ~g of a non-volatile solute is dissolved in 100 ~g of water, the vapour pressure is lowered by 2.25 10⁻¹ ~mm . If the vapour pressure of water at 20^ C is 17.5 ~mm , what is the molecular weight of the solute?

Options

  1. A206
  2. B302
  3. C350
  4. D276

Correct answer

C. 350

Step-by-step solution

Given, weight of non-volatile solute, w=25 ~g Weight of solvent, W=100 ~g Lowering of vapour pressure, p^ -p_s=0.225 ~mm Vapour pressure of pure solvent, p^ =17.5 ~mm Molecular weight of solvent ( H ₂ O ), M=18 ~g Molecular weight of solute, m= ? According to Raoult's law aligned p^ -p_s p^ & = w M m W 0.225 17.5 & = 25 18 m 100 m & = 25 18 17.5 22.5 & =350 ~g aligned

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