Question 2 of 4 Map General Chemistry University Science Books 4th Edition prese

Question

Question 2 of 4 Map General Chemistry University Science Books 4th Edition presented by Sapling Learning Donald McQuarrie. Peter A. Rock Ethan Gallogly 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 1.78 g of quinine is dissolved in 25.0 g of cyclohexane, the freezing point of the solution is lowered by 4.58 °C. The freezing point and Kf constant for cyclohexane can be found here Calculate the molar mass of quinine. Number g mol o Previous Check Answer o Next Exit Hint

Explanation / Answer

depression in F.P = Kf*m

Let the molar mass of quinine = 'M' g/mole

Thus, moles of quinine in 1.78 g of it = mass/molar mass = 1.78/M

molality of the solution = moles of quinine/mass of solvent in kg = (1.78/M)/0.025 = 71.2/M

Now, 4.58 = 20.8*(71.2/M)

or, M = molar mass of quinine = 323.354 g/mole

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