Molality (13.1.3)

Question 1

 Molality is a unit of concentration that does not depend on temperature.

Answer 1

 Molality is a unit of concentration that does not depend on temperature.

Question 2

 The density and molarity of a solution together provide enough information to find
the molality of a solution.

Answer 2

 The density and molarity of a solution together provide enough information to find
the molality of a solution.

Question 3

Suppose that you have 0.534 moles of solute in 0.430 L of water. What is the molality of the solution? Assume that the density of water is 1.000 g / mL.

Answer 3

1.24 mol / kg (C)

Question 4

A battery acid solution has a molarity of 3.83 M, a molar mass of 98.08 g / mol and a density of 1.25 g / mL. What is the mass of the solvent in one liter of solution?

Answer 4

0.874 kg (C)

Question 5

A solution is made by dissolving 33.7 g of MgCl2 and in 0.35 L of H2O. What are the mass of the solvent and the number of moles of the solute, respectively, in the solution? The density of water is 1.00 g / mL.

Answer 5

0.35 kg H2O; 0.354 mol MgCl2 (C)

Question 6

Which of the following statements about molarity or molality is not true?

Answer 6

Molarity is sometimes more helpful because it is independent of volume and not sensitive to changes in temperature. (A)

Question 7

Suppose that you have a solution of battery acid that has a molarity of 3.83 M. The molar mass of the solute is 98.08 g / mol. What is the mass of the solute in one liter of the battery acid? (Assume one liter is an exact number.)

Answer 7

0.376 kg (A)

Question 8

A solution has a molarity of 1.56 M and a density of 1.38 g / mL. The solute’s molar mass is 289.7 g / mol. What is the molality of the solution? Assume the density of the water is 1.00 g / mL.

Answer 8

1.68 mol / kg (A)

Question 9

The density of a 1.83 M aqueous solution of methanol is 0.976 g / mL. The molar mass of the solute is 32.04 g / mol. What is the molality of the solution?

Answer 9

2.00 mol / kg (A)

Question 10

What is the molality of a battery acid solution that has a molarity of 4.19 M? The density of the solution is 1.25 g / mL. The molar mass of the solute is 98.08 g / mol.

Answer 10

4.99 mol / k (B)

Question 11

Find the molality of an MgCl2 solution that has 19.8 g of solute in 0.65 L of H2O. The molar mass of MgCl2 = 95.22 g / mol MgCl2. Assume that the density of water is 1.00 g / mL.

Answer 11

0.32 mol / kg (B)

Question 12

What mass of potassium nitrate (KNO3 ) should be added to 5.00 × 102 g of H2O in order to make a 0.300 m KNO3 solution? The molar mass of KNO3 is 101.1 g / mol

Answer 12

15.2 g (C)