Q: A solution is prepared by mixing 0.20 mol of ethanol and 0.80 mol of water. What is the mole fraction of ethanol in the solution?

$$\chi_{\text{ethanol}} = \frac{0.20}{0.20 + 0.80} = 0.20$$

Question 1

Which of the following best describes why salt (NaCl) dissolves in water?

Accepted Answer

Because water molecules form ion-dipole interactions with Na+ and Cl- ions, overcoming the lattice energy of NaCl.

Question 2

A solution is prepared by dissolving 10.0 g of NaCl (molar mass = 58.44 g/mol) in 100.0 g of water. What is the molality ($$m) of $$the solution?

Accepted Answer

$$m = \frac{10.0}{58.44} \div 0.100 = 1.71\ m$$

Question 3

Which of the following statements about colligative properties is correct?

Accepted Answer

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

Question 4

Which intermolecular forces are present in seawater?

Accepted Answer

Hydrogen bonding, ion-dipole, and London dispersion forces.

Question 5

A saturated solution of sugar in water is at equilibrium. What will happen if more sugar is added?

Accepted Answer

The excess sugar will remain undissolved at the bottom.

Question 6

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

Accepted Answer

Oil is nonpolar and water is polar, so there are no favorable interactions between them.

Question 7

Which equation correctly represents Henry's Law for the solubility of a gas in a liquid?

Accepted Answer

$$S_g = k_H P_g$$

Question 8

A 0.50 molal aqueous solution of NaCl is prepared. Assuming complete dissociation, what is the expected van't Hoff factor ($$i) $$for NaCl?

Accepted Answer

$$i = 2$$

Question 9

Which of the following will increase the solubility of a gas in water?

Accepted Answer

Increasing the pressure of the gas above the solution.

Question 10

A solution is made by dissolving 2.0 moles of glucose (a non-electrolyte) in 1.0 kg of water. If the freezing point depression constant ($$K_f) $$for water is $$1.86\ ^\circ \mathrm{C}\cdot \mathrm{kg}/\mathrm{mol}$$, what is the expected freezing point of the solution?

Accepted Answer

$$-3.72\ ^\circ \mathrm{C}$$

Question 11

Which of the following best describes a hyperosmotic solution relative to a cell?

Accepted Answer

It has a higher osmotic pressure than the cell, causing water to flow out of the cell.

Question 12

Which of the following is an example of a solid solution?

Accepted Answer

Brass (copper and zinc)

Question 13

Which of the following best explains why the boiling point of a solution is higher than that of the pure solvent?

Accepted Answer

The solute lowers the vapor pressure of the solvent, requiring a higher temperature to boil.

Question 14

A solution is prepared by mixing 0.20 mol of ethanol and 0.80 mol of water. What is the mole fraction of ethanol in the solution?

Accepted Answer

$$\chi_{	ext{ethanol}} = \frac{0.20}{0.20 + 0.80} = 0.20$$

Question 15

Which of the following best describes a colloid?

Accepted Answer

A heterogeneous mixture with particles that do not settle out and scatter light.

Question 16

Which of the following is the correct formula for calculating osmotic pressure ($$\Pi) of a $$dilute solution?

Accepted Answer

$$\Pi = MRT$$

Question 17

Which of the following best explains why drinking seawater is dangerous for humans?

Accepted Answer

Seawater is hyperosmotic to body fluids, causing water to leave cells and leading to dehydration.

Question 18

Which of the following statements about miscibility is correct?

Accepted Answer

Two substances are miscible if they are always soluble in each other in all proportions.

Question 19

Which of the following is a correct statement about the energy changes during solution formation?

Accepted Answer

If the energy released in forming solute-solvent interactions is greater than the energy required to break solute-solute and solvent-solvent interactions, the process is exothermic.

Question 20

Which of the following best describes the Tyndall effect?

Accepted Answer

The scattering of light by particles in a colloid.

Solutions: Composition, Types, and Properties

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