Q: Which of the following correctly expresses molality ($$m) of a $$solution?

$$m = \frac{\text{mol solute}}{\text{kg solvent}}$$

Question 1

Which of the following best explains why hexane (C6H14) and pentane (C5H12) are mutually miscible in all proportions?

Accepted Answer

Their solution formation is driven primarily by entropy, as the energetic cost of breaking dispersion forces is minimal.

Question 2

A student dissolves NaOH in water and notices the beaker becomes warm. Which of the following statements best explains this observation?

Accepted Answer

The dissolution of NaOH in water is exothermic, so heat is released to the surroundings.

Question 3

Which of the following best describes the process of solution formation from an energetic perspective?

Accepted Answer

It involves overcoming solute–solute and solvent–solvent interactions (endothermic), and forming solvent–solute interactions (exothermic).

Question 4

Which equation correctly relates the free energy change ($$\Delta G) to $$enthalpy ($$\Delta H) $$and entropy ($$\Delta S) $$for solution formation?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 5

A solution is prepared by dissolving CO$$_2 in $$water under high pressure. What will happen to the solubility of CO$$_2 if $$the temperature is increased while keeping the pressure constant?

Accepted Answer

The solubility of CO$$_2$$ will decrease.

Question 6

Which of the following vitamins is most likely to be water-soluble based on its structure?

Accepted Answer

Vitamin C, because it contains multiple polar OH groups capable of hydrogen bonding.

Question 7

Which intermolecular force is primarily responsible for the dissolution of KF in water?

Accepted Answer

Ion-dipole interactions

Question 8

A solution is saturated when:

Accepted Answer

The rates of dissolution and precipitation of the solute are equal.

Question 9

Which of the following statements about the solubility of gases in liquids is correct?

Accepted Answer

The solubility of gases increases with increasing pressure.

Question 10

Which of the following best describes why water and pentane (C$$_5H$_{12}) do $$not mix?

Accepted Answer

Water is polar and pentane is nonpolar, so the energetic cost of breaking hydrogen bonds in water is not compensated by weak interactions with pentane.

Question 11

Which of the following correctly expresses molality ($$m) of a $$solution?

Accepted Answer

$$m = \frac{	ext{mol solute}}{	ext{kg solvent}}$$

Question 12

A chemist wants to purify a solid compound using recrystallization. Which property of solubility is most important for this process?

Accepted Answer

The solubility of solids increases with increasing temperature.

Question 13

Which of the following is the correct form of Henry’s Law for the solubility of a gas in a liquid?

Accepted Answer

$$	ext{Solubility} = k_H 	imes P_{	ext{gas}}$$

Question 14

Which of the following best explains why the dissolution of NH$$_4NO$_3 in $$water is used in instant cold packs?

Accepted Answer

The dissolution is endothermic, absorbing heat from the surroundings.

Question 15

A solution is prepared by dissolving 10 g of NaCl in 100 g of water at 25°C. If the solubility of NaCl at this temperature is 36.5 g/100 g water, what type of solution is formed?

Accepted Answer

Unsaturated solution

Question 16

Which of the following is a correct statement about the entropy change ($$\Delta S) $$during solution formation?

Accepted Answer

$$\Delta S is $$always positive because disorder increases.

Question 17

Which of the following best describes the relationship between the enthalpy of solution ($$\Delta H_{	ext{soln}}) $$and the likelihood of solution formation?

Accepted Answer

If $$\Delta H_{	ext{soln}} \u003c 0$$, solution formation is always favorable.

Question 18

A chemist wants to remove NH$$_3$$ from a mixture of NH$$_3$$ and N$$_2$$ using water. Which property of NH$$_3 is $$most useful for this separation?

Accepted Answer

NH$$_3$$ has a larger Henry’s constant ($$k_H) in $$water than N$$_2$$, so it is more soluble.

Question 19

Which of the following is the correct expression for molarity ($$M$$)?

Accepted Answer

$$M = \frac{	ext{mol solute}}{	ext{L solution}}$$

Solutions: Structure, Formation, and Properties (General Chemistry Study Notes)

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