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g Learning Engag x D og in x lua Calendar Blackboard Le xy UNC Chapel Hill -CHEM g.com/ibiscms/mod/ibis/view.php?id 2687222 Print Icalouletor Periodio Table Question 1 of 9 General Chemistry 4th Editon University Science Books presented by Saning Learning Quirine 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 1.72 g of quinine is dissolved in 25.0 g of freezing point of the solution is lowered by cyclohexane, the be found here. 442 C. The freezing point and Kr constant for cyclohexane can Calculate the molar mass of quinine. Number g/mol O previous ® Give up s view solution Check Answer 0 Next 4Exit

Explanation / Answer

Freezing point dTf,

dTf = -i.Kf.m

with,

dTf = 4.42 oC

Kf = -20.2 oC/m

i = 1

we get,

molality (m) = -4.42/1 x -20.2 = 0.22 mol

molality = 0.22 = moles/Kg of solvent = 1.72 g/0.025 kg x molar mass

So molar mass of quinine = 1.72/0.22 x 0.025 = 313 g/mol (or 312.73 g/mol unrounded value)

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