Question

Marks: 0/1 What is the freezing point of water made by dissolving 15.07 g of magnesium chloride in 93.88 g of water? The freezing point depression constant of water is 1 86 °C/m Answer Submit Incorrect Marks for this submission 1 18 Marks: 0/1 What is the freezing point of water made by dissolving 18.68 g of sodium chloride in 91.68 g of water? The freezing point depression constant of water is 1.36°C/m. Answer Submit Incorrect Marks for this submission: 0/1 19 What is the freezing point of water made by dissolving 50.54 g of sugar (C12H220.1) in 90.54 g of water? The freezing point depression constant of water is 1.86 °C/m. Marks: -11 Answer

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Answer 1

wherse, ks = troket When a non-volatile Solute is added in a Solvent then Change in freezing point, AT =k, mi a Kf = froeeting point depression Constant m = molality of solution (17) Number of moles of magnesium chloride a wee molar mass - 15.07 g 95.21 g/mol = 0.158 mol molality of the given solution = number of moles of Mgcd2 mass of solvent in kg 0.158 mol 0.09388 kg = 1.68 mol/kg AT=Kfm » Tsolvent - Tmixture=Kfm » 0°c - Tmixturse = 1.86 °C/m x 1.68 m > Tmixture = (-3.12 °C

• (18) Number Number of moles of NaCl = 18.68 g 58.44 g/mol = 0.319 mol Molality of the solution = 0.319 mol 0.09168 kg = 3.47 m AT = kem, > Tsolvent - Tmixture = Kfm, » 0°c - Tmixture = 1.860c/m x 3.47 m » Termixture = -6.15°C 19 Number of moles of sugar = 50.54 g 34 2.3 g/mol = 0.147 mod Molality of the solution = 0.147 mod 0.09054 kg = 1.62 m AT = Kfm, 7 Tsolvent - Tmixture = kfm, » 0°C - Tmixture = 1.86°C/m x 1.62 m - Tmixture = (-3.01 °c