t Introduction to Units of Concentration The composition of a solution can be ex
ID: 1023180 • Letter: T
Question
t Introduction to Units of Concentration The composition of a solution can be expressed in several different ways. Four of the mass of component x 100% mass moles of component mole fraction X totaTmoles of solution (M) molarity of soll molality (mn A solution was prepared by dissolving 35.0 g of KCl in 225 g of water Part A Calculate the mass percent of KCl in the solution. Express your answer with the appropriate units. 13.5 firm Submit Hints M Answers Give Up Review Part Correct Part B Calculate the mole fraction of the ionic species KCl in the solution. Express the concentration numerically as a mole fraction in decimal form. Submit Hints My Answers Give Up Review Part incorrect. Try Again; 5 attempts remaining Part C Calculate the molarity of KCl in the solution if the total volume of the solution is 239 mL. Express your answer with the appropriate units. Value Units Submit Hints My Answers Give Up Review Part incorrect; Try Again; 5 attempts remainingExplanation / Answer
A)
mass percentage = (mass of KCl / total mass) x 100
mass percentage = (35.0 g / (35.0 + 225.0 g) x 100 = 13.5 %
B)
mol fraction KCl = mole KCl / total moles
35.0 g KCl x (1 mol / 74.55 g) = 0.469 mol KCl
225 g H2O x (1 mol / 18.0 g) = 12.5 mol H2O
Total mol = 0.469 + 12.5 = 13.0 mol (sig figs to .1)
mol fraction KCl = 0.469 / 13.0 = 0.0361
C)
M = mol / L = 0.469 mol / 0.239 L = 1.96 M
D)
molality = mol KCl / kg H2O
molality = 0.469 mol / 0.225 kg H2O = 2.08 molal
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