Q: During the dissolution of NaCl in water, which process is exothermic?

Formation of hydration shells around Na\textsuperscript{+} and Cl\textsuperscript{–} ions.

Q: Which equation correctly represents the total enthalpy change when a solution forms?

$$\Delta H_{\text{soln}} = \Delta H_{\text{solute}} + \Delta H_{\text{solvent}} + \Delta H_{\text{mix}}$$

Q: A solution contains benzene and ethylene chloride at 50°C. The mole fraction of benzene is 0.6, vapor pressure of pure benzene is 268 mmHg, and ethylene chloride is 236 mmHg. What is the total vapor pressure?

$$P_{\text{total}} = 268 \times 0.6 + 236 \times 0.4 = 255.2$$ mmHg

Question 1

Which of the following statements best explains the principle 'like dissolves like' in the context of pharmaceutical solutions?

Accepted Answer

Substances with similar types of intermolecular forces dissolve in each other.

Question 2

During the dissolution of NaCl in water, which process is exothermic?

Accepted Answer

Formation of hydration shells around Na	extsuperscript{+} and Cl	extsuperscript{–} ions.

Question 3

A solid dissolves in a liquid in three steps. Which step is always exothermic?

Accepted Answer

Mixing of separated solute and solvent particles.

Question 4

Which equation correctly represents the total enthalpy change when a solution forms?

Accepted Answer

$$\Delta H_{	ext{soln}} = \Delta H_{	ext{solute}} + \Delta H_{	ext{solvent}} + \Delta H_{	ext{mix}}$$

Question 5

If the dissolution of a solid in water is endothermic, how does its solubility change with temperature?

Accepted Answer

Solubility increases as temperature increases.

Question 6

Why does the solubility of gases in liquids generally decrease with increasing temperature?

Accepted Answer

Because increased temperature increases kinetic energy, causing gases to escape.

Question 7

Which of the following best describes the effect of pressure on the solubility of gases in solids?

Accepted Answer

Solubility is proportional to pressure at constant temperature.

Question 8

A pharmaceutical scientist wants to increase the solubility of a gas in a solid before use. What should they do?

Accepted Answer

Lower pressure and increase temperature.

Question 9

Which of the following is an example of a completely miscible liquid pair?

Accepted Answer

Alcohol and water.

Question 10

According to Raoult's law, what is the partial vapor pressure of component A in an ideal solution?

Accepted Answer

$$P_A = X_A P_A^0$

Question 11

A solution contains benzene and ethylene chloride at 50°C. The mole fraction of benzene is 0.6, vapor pressure of pure benzene is 268 mmHg, and ethylene chloride is 236 mmHg. What is the total vapor pressure?

Accepted Answer

$$P_{	ext{total}} = 268 	imes 0.6 + 236 	imes 0.4 = 255.2$$ mmHg

Question 12

In an ideal solution of A and B, if $$X_A = 0.25$$, $$P_A^0$ = 60$$ mmHg, and $$P_B^0$ = 100$$ mmHg, what is the mole fraction of A in the vapor phase?

Accepted Answer

$$X(A) = 15/90 = 0.166$$

Question 13

Which statement is true about the vapor pressure of a mixture of completely immiscible liquids?

Accepted Answer

It is higher than the vapor pressure of each pure component.

Question 14

What is the effect of temperature on the miscibility of partially miscible liquids such as water and phenol?

Accepted Answer

There is a critical solution temperature above which the liquids are completely miscible.

Question 15

Which of the following best describes adsorption in the context of gases in solids?

Accepted Answer

Gas molecules are kept on the surface of the solid.

Question 16

Which property is NOT characteristic of an ideal solution of two completely miscible liquids?

Accepted Answer

The attractive forces between A and B are much weaker than those between AA or BB.

Question 17

Which of the following is a real-world example of a partially miscible liquid pair?

Accepted Answer

Water and phenol.

Question 18

If the lattice energy of a solid is greater than the solvation energy, what can be said about the dissolution process?

Accepted Answer

Dissolution is endothermic.

Question 19

Which factor does NOT affect the solubility of a gas in a solid?

Accepted Answer

Color of the solid.

Solutions and Their Properties: Solubility, Thermodynamics, and Raoult's Law

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