Q: Which equation correctly represents the calculation for molality ($$m$$)?

$$m = \frac{\text{moles of solute}}{\text{mass of solvent (kg)}}$$

Question 1

Why is it dangerous to drink seawater when stranded at sea?

Accepted Answer

Seawater is hypertonic, causing water to leave your cells by osmosis, leading to dehydration.

Question 2

Which of the following best describes osmosis?

Accepted Answer

The movement of solvent from low to high solute concentration through a semipermeable membrane.

Question 3

Which equation correctly represents the calculation for molality ($$m$$)?

Accepted Answer

$$m = \frac{	ext{moles of solute}}{	ext{mass of solvent (kg)}}$$

Question 4

A solution is prepared by dissolving 10 g of NaCl in 100 g of water. Which term best describes this solution if no more NaCl can dissolve at this temperature?

Accepted Answer

Saturated

Question 5

Which of the following is a colligative property?

Accepted Answer

Boiling point elevation

Question 6

What is the freezing point depression ($$\Delta T_f) $$for a solution made by dissolving 1.0 mol of NaCl in 1.0 kg of water? ($$K_f$$ for water = $$1.86\ ^\circ\mathrm{C}\cdot\mathrm{kg}/\mathrm{mol}$$, assume complete dissociation)

Accepted Answer

$$\Delta T_f = 3.72\ ^\circ\mathrm{C}$$

Question 7

Which of the following best explains why adding salt to ice causes the ice to melt at a lower temperature?

Accepted Answer

Salt decreases the freezing point of water by disrupting the equilibrium between solid and liquid phases.

Question 8

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

Accepted Answer

$$\Pi = iMRT$$

Question 9

A solution of glucose ($$C_6H_{12}O_6$) in water has a lower vapor pressure than pure water. This is an example of which colligative property?

Accepted Answer

Vapor pressure lowering

Question 10

Which of the following statements about Raoult's Law is correct?

Accepted Answer

Raoult's Law states that the vapor pressure of a solution is equal to the sum of the vapor pressures of the pure components multiplied by their mole fractions.

Question 11

Which of the following best describes a positive deviation from Raoult's Law?

Accepted Answer

The total vapor pressure is greater than predicted by Raoult's Law.

Question 12

Which of the following is true about entropy in the context of solution formation?

Accepted Answer

Entropy is a measure of the disorder or randomness of a system, and tends to increase when solutions form.

Question 13

A solution is prepared by dissolving 20.0 g of urea ($$CO(NH_2$)_2) in 200.0 g of $$ethanol ($$C_2H_5OH). If $$the boiling point elevation constant ($$K_b) $$for ethanol is $$1.22\ ^\circ\mathrm{C}\cdot\mathrm{kg}/\mathrm{mol}$$, what is the boiling point elevation ($$\Delta T_b$$)? (Molar mass of urea = 60.0 g/mol)

Accepted Answer

$$\Delta T_b = 0.33\ ^\circ\mathrm{C}$$

Question 14

Which of the following best describes a supersaturated solution?

Accepted Answer

A solution that contains more solute than it can theoretically hold at a given temperature.

Question 15

Which of the following is the correct formula for percent by mass?

Accepted Answer

$$	ext{Percent by mass} = \frac{	ext{mass of solute}}{	ext{mass of solution}} 	imes 100$$

Question 16

Which of the following is true about the effect of temperature on the solubility of most solid solutes in water?

Accepted Answer

Solubility increases with increasing temperature.

Question 17

Which of the following best explains why the vapor pressure of a solution is lower than that of the pure solvent?

Accepted Answer

The solute particles occupy surface sites, reducing the number of solvent molecules able to escape into the vapor phase.

Question 18

Which of the following is the correct expression for freezing point depression?

Accepted Answer

$$\Delta T_f = K_f m$$

Question 19

A solution contains 0.1 mol of NaCl and 0.1 mol of glucose in 1 kg of water. Which solution will have the higher boiling point?

Accepted Answer

The NaCl solution, because it produces more particles in solution.

Chapter 12: Solutions and Their Properties – General Chemistry Study Notes

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