Perspiration has a slight acidity because of the presence oflactic acid (C 3 H 6
ID: 676002 • Letter: P
Question
Perspiration has a slight acidity because of the presence oflactic acid (C3H6O3). Suppose weanalyze the perspiration of a chemistry student running late toclass. If the density of the perspiration were 1.23 g/mL and the mass percent lactic acid were foundto be 4.82%, what would you calculate asthe mole fraction, molarity, and molality of the lactic acid?(Assume that the perspiration contains only lactic acid andwater.)______________mole fraction molarity
____________ M
molality
____________ m
Perspiration has a slight acidity because of the presence oflactic acid (C3H6O3). Suppose weanalyze the perspiration of a chemistry student running late toclass. If the density of the perspiration were 1.23 g/mL and the mass percent lactic acid were foundto be 4.82%, what would you calculate asthe mole fraction, molarity, and molality of the lactic acid?(Assume that the perspiration contains only lactic acid andwater.)
______________mole fraction molarity
____________ M
molality
____________ m
Explanation / Answer
We Know that : Xlacticacid = number of moles of lactic acid/ Total number of moles of solution = 4.82 gm / 90 g / mole / 4.82 gm/ 90 g / mole + 95.18 gm / 108 gm/mole = 0.05728 Molarity of Lacticacid = Number of moles of Lactic acid / Volume of the solution L = [ 4.82 g / 90 g / mole / weight of thesubstance / density ( ml ) ] x 1000 = [ 4.82 g / 90 g / mole / 95.18 g/ 1.23 g / ml ] * 1000 = 0.6920 M Molality ofthe Lactic acid = number of moles of lacticacid / weight of the solvent Kg = 0.05355 / 95.18 g / 1000 = 0.56267 molal. Perspirationcontains ortho- cresol or para-cresol as thesolvent.Related Questions
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