Q: A solution is prepared by dissolving 8.00 g of KCl in 42.00 g of water, resulting in a total solution mass of 50.00 g. What is the mass/mass percent of KCl in the solution?

$$\frac{8.00}{50.00} \times 100\% = 16.0\%$$

Q: A solution is prepared by dissolving 10.0 g of urea ($$CH_4N_2O$$, molar mass = 60.06 g/mol) in 150.0 g of water. What is the boiling point of the solution? ($$K_b = 0.51\, ^\circ C/m$$ for water)

$$\Delta T_b = 0.51 \times \frac{10.0/60.06}{0.150} = 0.57^\circ C$$; Boiling point = $$100.00^\circ C + 0.57^\circ C = 100.57^\circ C$$

Q: Which equation correctly expresses molarity ($$M$$)?

$$M = \frac{\text{moles of solute}}{\text{liters of solution}}$$

Question 1

Which statement best explains why water is considered the most common solvent in chemistry?

Accepted Answer

Water forms hydrogen bonds, is polar, and can dissolve many ionic and polar substances.

Question 2

A solution is prepared by dissolving 8.00 g of KCl in 42.00 g of water, resulting in a total solution mass of 50.00 g. What is the mass/mass percent of KCl in the solution?

Accepted Answer

$$\frac{8.00}{50.00} 	imes 100\% = 16.0\%$$

Question 3

Which of the following best describes a supersaturated solution?

Accepted Answer

A solution that contains more than the maximum amount of solute that will dissolve at a specific temperature and is unstable.

Question 4

Which of the following solutes would be more soluble in benzene ($$C_6H_6) $$than in water?

Accepted Answer

$$CCl_4$$

Question 5

A solution is made by dissolving 170.1 g of glucose ($$C_6H_{12}O_6$, molar mass = 180.2 g/mol) in enough water to make 1.00 L of solution. The density of the solution is 1.062 g/mL. What is the molality of the solution?

Accepted Answer

$$\frac{170.1\,g}{180.2\,g/mol} = 0.944\,mol$$; $$1.062\,g/mL 	imes 1000\,mL = 1062\,g$$; $$1062\,g - 170.1\,g = 891.9\,g = 0.892\,kg$$; $$m = \frac{0.944}{0.892} = 1.06\,m$$

Question 6

Which of the following statements about colligative properties is correct?

Accepted Answer

Colligative properties depend only on the number of solute particles in solution.

Question 7

A solution is prepared by dissolving 10.0 g of urea ($$CH_4N_2O$$, molar mass = 60.06 g/mol) in 150.0 g of water. What is the boiling point of the solution? ($$K_b = 0.51\, ^\circ C/m$$ for water)

Accepted Answer

$$\Delta T_b = 0.51 	imes \frac{10.0/60.06}{0.150} = 0.57^\circ C$$; Boiling point = $$100.00^\circ C + 0.57^\circ C = 100.57^\circ C$$

Question 8

Which of the following best explains why oil and water do not mix?

Accepted Answer

The enthalpy of solution ($$\Delta H_{soln}) is $$large and positive because it takes considerable energy to overcome hydrogen bonding in water and there is little interaction between nonpolar oil and polar water.

Question 9

Which equation correctly expresses molarity ($$M$$)?

Accepted Answer

$$M = \frac{	ext{moles of solute}}{	ext{liters of solution}}$$

Question 10

A solution is made by dissolving 32.0 g of methanol ($$CH_3OH$$, molar mass = 32.04 g/mol) in 90.0 g of water (molar mass = 18.02 g/mol). What is the mole fraction of methanol in the solution?

Accepted Answer

$$\chi_{CH_3OH} = \frac{32.0/32.04}{(32.0/32.04)+(90.0/18.02)} = 0.167$$

Question 11

Which of the following is true about the effect of temperature on the solubility of gases in liquids?

Accepted Answer

The solubility of gases in liquids decreases as temperature increases.

Question 12

According to Raoult's Law, what is the vapor pressure of a solution made by dissolving a nonvolatile solute in a solvent?

Accepted Answer

It is lower than the vapor pressure of the pure solvent and is given by $$P_{solution} = X_{solvent} P^\circ_{solvent}.$$

Question 13

A solution is prepared by dissolving 52.9 g of $$CuCl_2 ($$molar mass = 134.45 g/mol) in 789.6 g of water at 52°C. The vapor pressure of water at 52°C is 102.1 torr. What is the vapor pressure of the solution, considering $$CuCl_2$$ dissociates completely into 3 ions?

Accepted Answer

$$X_{water} = \frac{789.6/18.02}{(789.6/18.02)+(52.9/134.45)	imes3}$$; $$P_{solution} = X_{water} 	imes 102.1$$; $$P_{solution} \approx 99.2$$ torr

Question 14

Which of the following best describes a colloid?

Accepted Answer

A dispersion of particles much larger than normal solute molecules throughout another substance.

Question 15

Which equation is used to calculate the osmotic pressure ($$\Pi) of a $$solution?

Accepted Answer

$$\Pi = iMRT$$

Question 16

A semipermeable membrane separates a 10% (m/v) NaCl solution (A) from a 5% (m/v) NaCl solution (B). What will happen?

Accepted Answer

Water will flow from solution B to solution A.

Question 17

Which of the following is an example of a miscible pair of liquids?

Accepted Answer

Ethanol and water

Question 18

Which of the following statements about isotonic, hypotonic, and hypertonic solutions is correct?

Accepted Answer

Isotonic solutions exert the same osmotic pressure as red blood cells.

Chapter 13: Properties of Solutions – General Chemistry Study Notes

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