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Solutions

Short Answer Type

141. If the solubility product of CuS is 6 x 10^–16, calculate the maximum molarity of CuS in aqueous solution.

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142. Calculate the mass percentage of aspirin (C₉H₈O₄) in acetonitrile (CH₃CN) when 6.5 of C₉H₈O₄ is dissolved in 400 g of CH₃CN.

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Long Answer Type

143. Calculate the molarity of 1 litre solution of 93% H₂SO₄ (weight/volume). The density of solution is 1.84 gm L^–1.

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Short Answer Type

144. Calculate the amount of benzoic acid (C₆H₅COOH) required for preparing 250 mL of 0.15 M solution in methanol.

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145. Calculate the depression in the freezing of water when 10 g of CH₃CH₂CHCICOOH is added to 250 g of water. K_a = 1.4 x 10^–3, K_f= 1.86 K kg moL^–1.

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146. Nalorphene (C₁₉ H₂₁ NO₃) similar to morphine, is used to combat withdrawl symptoms in narcotic users. Dose of nalophene generally given is 1.5 mg. Calculate the mass of 1.5 x10^–3 m aqueous solution required for the above dose.

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147. Vapour pressure of water at 293 K is 17.535 mm Hg. Calculate the vapour pressure of water at 293 K when 25 g of glucose is dissolved in 450 g of water.

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148. Henry's law constant for the molality of methane in benzene at 298 K is 4.27 x 10⁵mm Hg. Calculate the solubility of methane in benzene at 298 K under 760 mm Hg.

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149. Determine the amount of CaCl₂(i = 2.47) dissolved in 2.5 litre of water such that its osmotic pressure is 0.75 atm at 27⁰C.

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150. Determine the osmotic pressure of a solution prepared by dissolving 25 mg of K₂SO₄ in 2 litre of water at 25⁰ C, assuming that it is completely dissociated.

Answer:
When K₂SO₄ is dissolved in water , K⁺ and

{SO}_{4}^{2 -}

ion produced

K_{2} {SO}_{4} \to 2 K^{+} + {SO}_{4}^{2 -}

total number of ion produced 3
therfore, i = 3
given that

w = 25 mg = 0.025g
T = 25⁰C + 273 = 298 K
Also we know that
R = 0.0821 L atm K^-1 mol^-1
M= (2 x39)+(1x 32)+(4x16)

Osmotic pressure,