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11. Calculate the mass of ascorbic acid (Vitamin C, C₆H₈O₆) to be dissolved in 75 g of acetic acid to lower its melting point by 1.5 ⁰C. K_f= 3.9 k kg mol^–1.

Solution:
Mass of acetic acid W₁= 75g
Molar mass o_{f $C_{6} H_{8} O_{6}$

$= 6 \times 12 + 8 \times 1 + 6 \times 16 = 72 + 8 + 96 = 176 g {mol}^{- 1}$}lowering of melting point ,
_{$∆ T_{f} = 1.5 k We know that : ∆ T_{f} = \frac{K_{f} \times w_{2} \times 1000}{M_{2} \times w_{1}} = w_{2} = \frac{∆ T_{f} \times M_{2} \times w_{1}}{K_{f} \times 1000} = \frac{1.5 \times 176 \times 75}{3.9 \times 1000} = 5.08 g approx .$}

Hence, 5.08 g of ascorbic acid is needed to be dissolved.

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12. Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0 g of polymer of molar mass 185,000 in 450 mL at 37⁰C.

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Short Answer Type

13. Suppose a solid solution is formed between two substances, one whose particles are very large and the other whose particles are very small. What kind of solid solution is this likely to be?

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14. Amongst the following compunds identify which are insoluble, partially soluble and highly soluble in water?
(i) phenol (ii) toluene (iii) formic acid (iv) ethylene glycol (v) chloroform, (vi) pentanol.

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15. Two liquids A and B boils at 145⁰C and 190⁰C respectively. Which of them has a higher vapour pressure at 80⁰C ?

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16. Define ‘mole fraction’ of a substance in a solution.

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17. What is expected value of Van’t Hoff factor for K₃ [Fe(CN)₆] in dilute solution?

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18. State the formula relating pressure of a gas with its mole fraction in a liquid solution in contact with it.

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19. What would be the value of Van’t Hoff factor for a dilute solution of K₂SO₄ in water?

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20. In the determination of molar mass of A⁺B^– using a colligative property, what may be the value of Van’t Hoff factor if the solute is 50% dissociated?

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Previous Year Papers

Test Series

Test Yourself

Long Answer Type

11. Calculate the mass of ascorbic acid (Vitamin C, C6H8O6) to be dissolved in 75 g of acetic acid to lower its melting point by 1.5 0C. Kf= 3.9 k kg mol–1.

Short Answer Type

11. Calculate the mass of ascorbic acid (Vitamin C, C₆H₈O₆) to be dissolved in 75 g of acetic acid to lower its melting point by 1.5 ⁰C. K_f= 3.9 k kg mol^–1.