Question 1

Which of the following best explains why NaCl dissolves readily in water but not in hexane?

Accepted Answer

NaCl forms strong ion-dipole interactions with water, which are absent in hexane.

Question 2

A solution is prepared by dissolving 1.06 g of NaNO$$_3 in $$enough water to make 125 mL of solution. What is the molarity of the solution? (Molar mass of NaNO$$_3 = 85.0 g/$$mol)

Accepted Answer

$$0.100\ \mathrm{M}$$

Question 3

Which of the following statements about the energetics of solution formation is correct?

Accepted Answer

If the hydration energy of the ions is greater than the lattice energy, the dissolution process is exothermic.

Question 4

At 60°C, a solution contains 38 g of KCl per 100 g of water. If the solubility of KCl at this temperature is 45 g per 100 g of water, what type of solution is this?

Accepted Answer

Unsaturated

Question 5

A solution is prepared by dissolving 2.1 g of dioxin in enough water to make 1.34 L of solution. What is the concentration of dioxin in g/L?

Accepted Answer

$$1.57\ \mathrm{g/L}$$

Question 6

Which of the following best describes the effect of adding a nonvolatile solute to a solvent?

Accepted Answer

The vapor pressure of the solution decreases compared to the pure solvent.

Question 7

A solution is prepared by dissolving 1.3 g of NaNO$$_3 in 124 g of $$water. What is the molality of the solution? (Molar mass of NaNO$$_3 = 85.0 g/$$mol)

Accepted Answer

$$0.122\ \mathrm{mol/kg}$$

Question 8

Which of the following solutions will have the highest vapor pressure at the same temperature?

Accepted Answer

A solution of a nonvolatile solute in a volatile solvent with the lowest solute concentration.

Question 9

Calculate the freezing point of a solution made by dissolving 45 g of KCl in 100 g of water. ($$K_f$$ for water = $$1.86\ ^\circ\mathrm{C}\cdot\mathrm{kg}/\mathrm{mol}$$, molar mass of KCl = 74.6 g/mol, assume complete dissociation.)

Accepted Answer

$$-22.5\ ^\circ\mathrm{C}$$

Question 10

Which of the following best explains why CF$$_4(a) is $$less soluble in water than CF$$_3CH$_2OH$$?

Accepted Answer

CF$$_4(a) is $$nonpolar and cannot form hydrogen bonds with water, while CF$$_3CH$_2OH is $$polar and can.

Question 11

A solution is prepared by dissolving 117 mL of acetic acid (density = 1.05 g/mL) in enough water to make 1.00 L of solution. What is the molarity of acetic acid? (Molar mass = 60.05 g/mol)

Accepted Answer

$$2.05\ \mathrm{M}$$

Question 12

Which of the following is the correct calculation for the mole fraction of C$$_6H$_{14} in a $$solution containing 133 torr vapor pressure of C$$_6H$_{14}$$ and a total vapor pressure of 340 torr?

Accepted Answer

$$X_{C_6H_{14}} = \frac{133}{340}$$

Question 13

A solution is prepared by dissolving 0.628 mol of NaOCl in enough water to make 1.00 L of solution. What is the molarity of the solution?

Accepted Answer

$$0.628\ \mathrm{M}$$

Question 14

Which of the following best describes a supersaturated solution?

Accepted Answer

A solution that contains more solute than is present in a saturated solution at a given temperature.

Question 15

If the hydration enthalpy of LiCl is $$-871\ \mathrm{kJ/mol}$$ and that of NaCl is $$-765\ \mathrm{kJ/mol}$$, which salt releases more energy upon dissolving in water and why?

Accepted Answer

LiCl, because its hydration enthalpy is more negative.

Question 16

A solution is prepared by dissolving 1.4 x $$10^{-4}$$ mol of a solute in 1.00 mL of water. What is the molarity of the solution?

Accepted Answer

$$0.14\ \mathrm{M}$$

Question 17

Which of the following is a correct statement about colligative properties?

Accepted Answer

They depend on the number of solute particles, not their identity.

Question 18

A solution is prepared by dissolving 38 g of KCl in 100 g of water at 60°C. If the solubility at this temperature is 45 g per 100 g of water, what will happen if the solution is cooled to 0°C, where the solubility is 28 g per 100 g of water?

Accepted Answer

12 g of KCl will precipitate out of solution.

Question 19

Which of the following best explains why the dissolution of some ionic solids in water is exothermic?

Accepted Answer

The energy released from hydration of the ions is greater than the energy required to break the ionic lattice.

Solutions and Colligative Properties: General Chemistry Study Notes

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