Boiling Point Elevation Formula and Worked Examples

📚 Boiling Point Elevation: Quick Study Guide

• 🌡️ Boiling point elevation is a colligative property, meaning it depends on the number of solute particles in a solution, 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 the 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).
• 💧 Molality (m) is calculated as: $$m = \frac{\text{moles of solute}}{\text{kilograms of solvent}}$$.
• 🧊 The van't Hoff factor ($i$) is 1 for non-electrolytes (do not dissociate), and for electrolytes, it's approximately the number of ions formed per formula unit (e.g., $NaCl$ has $i=2$).

Practice Quiz

1. Question 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 number of solute particles.
   4. D) A property that is independent of the solution composition.
2. Question 2: Which of the following is the correct formula for boiling point elevation?
   1. A) $$\Delta T_b = K_b / (i * m)$$
   2. B) $$\Delta T_b = i * K_b * m$$
   3. C) $$\Delta T_b = i * K_b / m$$
   4. D) $$\Delta T_b = K_b * m$$
3. Question 3: 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 the solute dissociates into.
   4. D) The mass of the solvent.
4. Question 4: What is the boiling point elevation of a solution containing 0.5 mol of $NaCl$ in 200g of water ($K_b = 0.512 \frac{°C \cdot kg}{mol}$)?
   1. A) 2.56 °C
   2. B) 5.12 °C
   3. C) 10.24 °C
   4. D) 1.28 °C
5. Question 5: What is the molality of a solution containing 10g of glucose (molecular weight = 180 g/mol) in 500g of water?
   1. A) 0.11 m
   2. B) 0.22 m
   3. C) 0.33 m
   4. D) 0.44 m
6. Question 6: Which of the following solutes would you expect to have the largest van't Hoff factor?
   1. A) Glucose ($C_6H_{12}O_6$)
   2. B) Sodium Chloride ($NaCl$)
   3. C) Aluminum Chloride ($AlCl_3$)
   4. D) Sucrose ($C_{12}H_{22}O_{11}$)
7. Question 7: If a solution of 1 mol of a non-electrolyte in 1 kg of water has a boiling point elevation of 0.512 °C, what is the ebullioscopic constant ($K_b$) of water?
   1. A) 0.256 °C kg/mol
   2. B) 0.512 °C kg/mol
   3. C) 1.024 °C kg/mol
   4. D) 0.768 °C kg/mol