Question 15 of 22 Map General Chemistr University Science Books presented by Sap
ID: 806052 • Letter: Q
Question
Question 15 of 22 Map General Chemistr University Science Books presented by Sapling Lea Donald McQuarrie. Peter A Rock .Ethan Gallogly nthol is a crystalline substance with a peppermint taste and odor. When 1.18 g of menthol is dissolved in 25.0 g of cyclohexane, the freezing point of the solution is lowered by 6.30 °C. The freezing point and Kf constant for cyclohexane can be found here. Calculate the molar mass of menthol. Number g/mol Previous Give up & View Solution Check Answer Next xit ® 8 Hint Start by finding the molality, m (or b), of the solution using AT K, m where AT is the freezing-point depression, and Kf is a constant unique to the solvent.Explanation / Answer
Depression of freezing point is expressed as
?Tf = molality * Kf * i
Kf = freezing point constant [ cryoscopic constant ]
i = Van't Hoff factor
?Tf given as6.3 degc, molality of solute is{ [ 1.18/m ] / 25 } * 1000 = 47.2 / m where m is molar mass
g / mol of quinine , Kf is given as 20.8, Vant hoff factor for quinine is 1,
therefore,6.3 = 47.2/m * 20.8 or m =47.2*20.8/6.3 this equals to 155.83
Answer therefore is molar mass of quinine is 155.83 g/ mol