Rucete ✏ AP Chemistry In a Nutshell
8. Solutions — Practice Questions 2
This chapter introduces the properties and behaviors of solutions, including solubility, electrolytes, and the effects of temperature and pressure on concentration.
(Multiple Choice — Click to Reveal Answer)
1. Which of the following best describes a homogeneous mixture?
(A) Sand and water
(B) Oil and vinegar
(C) Salt dissolved in water
(D) Ice cubes in soda
Answer
(C) — A homogeneous mixture has uniform composition, like saltwater.
2. Which of the following solutes would most likely dissolve in hexane, a nonpolar solvent?
(A) NaCl
(B) CH₃OH
(C) I₂
(D) NH₃
Answer
(C) — I₂ is nonpolar and dissolves in nonpolar solvents (like dissolves like).
3. What is the term for the process of surrounding solute particles with solvent molecules?
(A) Condensation
(B) Crystallization
(C) Solvation
(D) Ionization
Answer
(C) — Solvation is the interaction between solute and solvent particles.
4. Which of the following is NOT a colligative property?
(A) Vapor pressure lowering
(B) Boiling point elevation
(C) Freezing point depression
(D) Molarity
Answer
(D) — Colligative properties depend on the number of particles, not concentration units.
5. Which of the following is most likely to form a conductive solution?
(A) CH₃CH₂OH
(B) Na₂SO₄
(C) C₆H₁₂O₆
(D) CCl₄
Answer
(B) — Sodium sulfate is an ionic compound that dissociates into ions in water.
6. Which factor does NOT increase the rate of dissolution of a solid in a liquid?
(A) Stirring
(B) Heating
(C) Using smaller solute particles
(D) Increasing atmospheric pressure
Answer
(D) — Pressure has little to no effect on solid solubility.
7. What is the main reason gases are less soluble in warm water?
(A) Gases form solids at high temperature
(B) Kinetic energy helps gases escape the solution
(C) Solids block solubility
(D) Gas particles lose energy
Answer
(B) — Higher kinetic energy allows gas particles to escape into the air.
8. Which solute-solvent combination is least likely to result in a solution?
(A) Polar solute in polar solvent
(B) Ionic solute in water
(C) Nonpolar solute in nonpolar solvent
(D) Polar solute in nonpolar solvent
Answer
(D) — Polar and nonpolar substances typically don’t mix well.
9. Which solution is the most concentrated?
(A) 1 mol in 1 L
(B) 2 mol in 4 L
(C) 0.5 mol in 0.25 L
(D) 3 mol in 6 L
Answer
(C) — 0.5 mol / 0.25 L = 2.0 M, which is the highest.
10. Which of the following best describes why ionic compounds dissolve in water?
(A) Water molecules replace solute ions
(B) Water’s polarity disrupts ionic bonds
(C) Water evaporates around the ions
(D) Ionic bonds become covalent in water
Answer
(B) — The polar water molecules interact with and separate ions via ion-dipole forces.
11. What is the total number of ions formed when one formula unit of MgCl₂ dissolves?
(A) 1
(B) 2
(C) 3
(D) 4
Answer
(C) — MgCl₂ → Mg²⁺ + 2Cl⁻ → 3 total ions.
12. Which of the following is the best definition of molarity?
(A) Moles of solute per kg of solvent
(B) Moles of solute per liter of solution
(C) Grams of solute per mL of solution
(D) Moles of solvent per liter of solute
Answer
(B) — Molarity (M) = mol solute / L of total solution.
13. Which factor will NOT change the molarity of a solution?
(A) Adding water
(B) Evaporating water
(C) Increasing solute amount
(D) Increasing temperature
Answer
(D) — Molarity depends on volume and amount of solute, not directly on temperature.
14. What is the main force responsible for the hydration of ions in water?
(A) Hydrogen bonding
(B) Dipole-dipole interactions
(C) Ion-dipole interactions
(D) Dispersion forces
Answer
(C) — Ion-dipole interactions occur between ions and polar water molecules.
15. In a lab, 25.0 g of KNO₃ is added to 100 g of water at 60°C and completely dissolves. What does this indicate about the solution?
(A) It’s unsaturated
(B) It’s saturated
(C) It’s supersaturated
(D) It’s a colloid
Answer
(A) — If all the solute dissolves, the solution is unsaturated at that temperature.
16. What type of solution forms when more solute is added than can dissolve at a given temperature?
(A) Dilute
(B) Unsaturated
(C) Supersaturated
(D) Saturated
Answer
(C) — Supersaturated solutions contain more solute than normally possible and are unstable.
17. Which of the following will decrease the freezing point of water the most?
(A) 0.5 M glucose
(B) 0.5 M NaCl
(C) 0.5 M CaCl₂
(D) 0.5 M CH₃OH
Answer
(C) — CaCl₂ dissociates into 3 particles, producing the greatest freezing point depression.
18. Which term describes the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature?
(A) Concentration
(B) Saturation
(C) Solubility
(D) Molarity
Answer
(C) — Solubility is the maximum solute amount that can dissolve under specific conditions.
19. Which of the following solutes will conduct electricity in solution?
(A) Sucrose
(B) CH₃OH
(C) NaOH
(D) CCl₄
Answer
(C) — NaOH is a strong base and dissociates completely into ions in water.
20. Which of the following statements is true about weak electrolytes?
(A) They completely ionize in solution
(B) They do not dissolve in water
(C) They ionize only partially
(D) They are insoluble in polar solvents
Answer
(C) — Weak electrolytes like HF only partially ionize in solution.
21. A 0.5 M NaCl solution and a 0.5 M MgCl₂ solution are prepared. Which has more total ions per liter?
(A) NaCl
(B) MgCl₂
(C) Both equal
(D) Not enough info
Answer
(B) — NaCl gives 2 ions; MgCl₂ gives 3 ions per formula unit → more particles per mole.
22. What happens when a solute is added to a solvent and the solution's vapor pressure decreases?
(A) Freezing point increases
(B) Boiling point decreases
(C) Boiling point increases
(D) Vapor pressure remains constant
Answer
(C) — Lower vapor pressure causes a rise in boiling point (boiling point elevation).
23. Which is the correct order of decreasing solubility of gases in water (highest to lowest)?
(A) High temp > medium temp > low temp
(B) Low temp > high temp > medium temp
(C) Low temp > medium temp > high temp
(D) Temperature does not matter
Answer
(C) — Gas solubility decreases with increasing temperature.
24. What kind of compounds are considered nonelectrolytes?
(A) Ionic compounds
(B) Strong acids
(C) Covalent compounds that don’t ionize
(D) Salts
Answer
(C) — Covalent compounds like glucose or ethanol dissolve without ionizing.
25. Which of the following statements is true about molality?
(A) It depends on temperature
(B) It uses volume of solvent
(C) It uses mass of solvent
(D) It changes with atmospheric pressure
Answer
(C) — Molality is defined as moles of solute per kilogram of solvent and is temperature-independent.
26. Which equation represents the relationship described by Henry’s Law?
(A) PV = nRT
(B) C = kP
(C) P = kC
(D) C = k/T
Answer
(B) — Henry’s Law: solubility (C) is directly proportional to gas pressure (P).
27. A student prepares a solution by dissolving 20 g of NaOH in 100 mL of water. What will be the effect on the solution’s temperature?
(A) Decreases
(B) Stays the same
(C) Increases
(D) Depends on stirring
Answer
(C) — Dissolution of NaOH is exothermic; temperature increases.
28. Which compound would have the greatest effect on boiling point elevation for the same molarity?
(A) NaCl
(B) CaCl₂
(C) CH₃OH
(D) NaNO₃
Answer
(B) — CaCl₂ dissociates into 3 ions, more particles → greater boiling point elevation.
29. Which statement is true regarding the enthalpy change of solution for an endothermic process?
(A) ΔH < 0
(B) ΔH = 0
(C) ΔH > 0
(D) Cannot be determined
Answer
(C) — Endothermic processes absorb heat, so ΔH is positive.
30. What is the role of entropy in the dissolution of solutes?
(A) It decreases solubility
(B) It opposes the mixing process
(C) It favors solute dispersion
(D) It only applies to solids
Answer
(C) — Greater entropy (more disorder) favors the formation of solutions.
31. If a saturated solution at 60°C is cooled to 30°C without forming a precipitate, it becomes:
(A) Unsaturated
(B) Supersaturated
(C) Diluted
(D) Crystalline
Answer
(B) — Cooling without crystallization leads to a supersaturated solution.
32. Which of the following explains why some ionic compounds are insoluble in water?
(A) High vapor pressure
(B) Strong lattice energy not overcome by hydration energy
(C) Low molar mass
(D) Large entropy increase
Answer
(B) — Insoluble salts have lattice energy too large to be compensated by hydration energy.
33. What is the primary driving force in the dissolution of gases in liquids under high pressure?
(A) Increased lattice energy
(B) Lower entropy
(C) More collisions of gas molecules with liquid surface
(D) Hydrogen bonding
Answer
(C) — Higher pressure = more gas particles forced into solution due to collisions.
34. Why is molality used in boiling point elevation calculations instead of molarity?
(A) Molarity is more accurate
(B) Volume changes with temperature, but mass doesn't
(C) Molality is based on ion charges
(D) Molality uses weaker units
Answer
(B) — Volume (used in molarity) changes with temperature; mass (used in molality) does not.
35. Which of the following would most likely form a colloid rather than a true solution?
(A) Salt in water
(B) Sugar in water
(C) Milk
(D) Ethanol in water
Answer
(C) — Milk is a colloid; it contains dispersed particles too large for a true solution.
36. What is the relationship between pressure and gas solubility in liquids?
Answer
Gas solubility increases with pressure, according to Henry’s Law.
37. Why does stirring increase the rate of dissolution?
Answer
Stirring removes dissolved solute from the surface and brings fresh solvent into contact with the solute.
38. What does "like dissolves like" mean in chemistry?
Answer
Polar solvents dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes.
39. Define hydration energy.
Answer
Hydration energy is the energy released when ions are surrounded by water molecules.
40. What is a dynamic equilibrium in a saturated solution?
Answer
It’s when the rate of dissolution equals the rate of crystallization of solute particles.
41. Name a strong acid that acts as a strong electrolyte in solution.
Answer
HCl (hydrochloric acid).
42. What does “miscible” mean?
Answer
Two liquids that can dissolve completely in each other.
43. Give an example of a nonelectrolyte and explain why.
Answer
Glucose — it dissolves in water but doesn’t ionize or conduct electricity.
44. Why are ionic compounds more soluble in polar solvents?
Answer
Because polar solvents stabilize the ions formed, overcoming lattice energy.
45. What is a colloid?
Answer
A heterogeneous mixture with particles larger than solution particles but too small to settle out.
46. Define "solution concentration".
Answer
The amount of solute dissolved in a given quantity of solvent or solution.
47. What type of interparticle force is involved when sugar dissolves in water?
Answer
Hydrogen bonding between sugar molecules and water.
48. Why doesn’t molality change with temperature?
Answer
Because it’s based on mass, which does not expand or contract with temperature.
49. Give one reason why temperature affects solubility of solids in liquids.
Answer
Higher temperatures increase molecular motion, helping solute particles separate and dissolve.
50. How can you visually identify a supersaturated solution?
Answer
It appears clear but forms crystals when disturbed or when a seed crystal is added.