AP Chemistry Questions on Boiling Point Elevation: Test Your Knowledge

📚 Quick Study Guide

• 🌡️ Boiling Point Elevation is a colligative property, meaning it depends on the concentration of solute particles, not their identity.
• ⚗️ The formula for boiling point elevation is: $$\Delta T_b = i * K_b * m$$, where:
  • $$\Delta T_b$$ is the boiling point elevation.
  • $$i$$ is the van't Hoff factor (number of particles a solute dissociates into).
  • $$K_b$$ is the ebullioscopic constant (boiling point elevation constant) of the solvent.
  • $$m$$ is the molality of the solution (moles of solute per kilogram of solvent).
• 💧 Remember that molality (m) is calculated as: $$m = \frac{\text{moles of solute}}{\text{kilograms of solvent}}$$.
• 💡 To find the new boiling point, add the boiling point elevation to the original boiling point of the pure solvent: $$T_{b(solution)} = T_{b(solvent)} + \Delta T_b$$.
• 🧪 Ionic compounds (like NaCl) dissociate into ions in solution, so their *i* value is greater than 1. Covalent compounds (like sugar) usually do not dissociate, so their *i* value is 1.

Practice Quiz

1. What is a colligative property?
   1. A) A property that depends on the type of solute.
   2. B) A property that depends on the amount of solvent.
   3. C) A property that depends on the concentration of solute particles.
   4. D) A property that depends on the volume of the solution.
2. What does the van't Hoff factor (i) represent?
   1. A) The molality of the solution.
   2. B) The boiling point elevation constant.
   3. C) The number of particles a solute dissociates into in solution.
   4. D) The change in temperature of the solution.
3. If 1 mole of NaCl is dissolved in water, what is the van't Hoff factor (i)?
   1. A) 1
   2. B) 2
   3. C) 0.5
   4. D) 3
4. What is the formula for calculating boiling point elevation ($$\Delta T_b$$)?
   1. A) $$\Delta T_b = K_b * m$$
   2. B) $$\Delta T_b = i * K_b / m$$
   3. C) $$\Delta T_b = i * K_b * m$$
   4. D) $$\Delta T_b = i / (K_b * m)$$
5. What happens to the boiling point of a solution when a non-volatile solute is added?
   1. A) It decreases.
   2. B) It increases.
   3. C) It stays the same.
   4. D) It fluctuates randomly.
6. A solution is made by dissolving 10 grams of glucose (C6H12O6) in 200 grams of water. What information is needed to calculate the boiling point elevation?
   1. A) Only the mass of glucose.
   2. B) The ebullioscopic constant of water and the van't Hoff factor of glucose.
   3. C) Only the ebullioscopic constant of water.
   4. D) The ebullioscopic constant of water, and the van't Hoff factor of water.
7. Which of the following solutions will have the highest boiling point? (Assume the same solvent and concentration for all solutions.)
   1. A) NaCl
   2. B) Glucose
   3. C) Sucrose
   4. D) KCl