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Quinine is a natural product extracted from the bark of the cinchona tree, which is native...

Quinine is a natural product extracted from the bark of the cinchona tree, which is native to South America. Quinine is used as an antimalarial agent. When 3.10 g of quinine is dissolved in 25.0 g of cyclohexane, the freezing point of the solution is lowered by 7.95 °C. The freezing point and Kf constant for cyclohexane can be found here. Calculate the molar mass of quinine.

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Expert Solution

Answer – We are given, mass of quinine = 3.10 g , mass of cyclohexane = 25.0 g , Freezing point is lowered , ∆Tf = 7.95oC

We know the formula,

∆Tf = Kf*m

So, m = ∆Tf /Kf

m = 7.95oC / 20.8oC.m-1

    = 0.382 m

So, molality = moles of solute / kg of solvent

So, moles of solute = molality * kg solvent

                               = 0.382 m * 0.025 kg

                               = 0.00956 moles

So, molar mass of quinine = 3.10 g / 0.00956 moles

                                           = 324.4 g/mol

queen_honey_blossom answered 2 years ago
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