Elevation of Boiling Point - UNSOLVED PRACTICE SET

Q7. Define elevation of boiling point. Derive the expression ΔTb = Kb · m for a dilute solution.

Q8. Calculate the boiling point of a solution containing 18 g of glucose in 500 g of water. (Kb for water = 0.512 K·kg/mol, boiling point of pure water = 100°C)

[Given: Molar mass of glucose = 180 g/mol]

Q9. Why is camphor used as a solvent in the Rast method for determining molar mass? What is special about camphor?

Q10. Explain why the elevation of boiling point is a colligative property and not a characteristic property of the solute.

Q11. Your mother uses a pressure cooker to cook dal faster. Explain how increased pressure raises the boiling point of water and why this cooks food faster.

Q12. Why does the addition of ethylene glycol to car radiator water prevent boiling over in summer?

Q13. Discuss elevation of boiling point in detail:

(a) Definition and explanation at the molecular level

(b) Derivation of the relationship ΔTb = Kb · m

(c) Definition and significance of ebullioscopic constant (Kb)

(d) Determination of molar mass using boiling point elevation

(e) Experimental methods: Landsberger's method and Cottrell's method

(f) Limitations and sources of error

Q14. Explain the factors affecting elevation of boiling point:

(a) Nature of solvent — how Kb varies with solvent properties

(b) Concentration of solute — linear relationship with molality

(c) Nature of solute — electrolytes vs. non-electrolytes (van't Hoff factor)

(d) Association and dissociation of solute particles

(e) Comparison of experimental and calculated values for different solutes

Q15. Elevation of boiling point has numerous practical applications in India. Discuss:

(a) Why pressure cookers are essential in Indian kitchens, especially at high altitudes (Himachal, Ladakh)

(b) The use of antifreeze (ethylene glycol) in car radiators across India's varied climate

(c) How sugar concentration is monitored in jaggery (gur) production using boiling point measurements

(d) The role of boiling point elevation in quality control of milk and dairy products in India

Q16. The boiling point elevation constant for benzene is 2.53 K·kg/mol. A solution of 2.0 g of a non-volatile solute in 100 g of benzene boils at 80.26°C. (Pure benzene boils at 80.10°C).

(a) Calculate the elevation of boiling point.

(b) Calculate the molality of the solution.

(c) Calculate the molar mass of the solute.

Q17. A car radiator contains 4.0 kg of water. To prevent freezing in winter and boiling in summer, 2.0 kg of ethylene glycol (C₂H₆O₂) is added.

(a) Calculate the boiling point of this coolant mixture. (Kb for water = 0.512 K·kg/mol)

(b) If the radiator operates at 1.5 atm pressure (boiling point of pure water at 1.5 atm ≈ 112°C), calculate the actual boiling point of the coolant at this pressure.

(c) Explain why ethylene glycol is preferred over methanol or ethanol as antifreeze.

[Given: Molar mass of ethylene glycol = 62 g/mol]

Q18. A jaggery (gur) manufacturing unit in Uttar Pradesh produces jaggery by concentrating sugarcane juice. The juice initially contains 15% sucrose by mass.

(a) Calculate the boiling point elevation when the juice is concentrated to 60% sucrose. (Kb for water = 0.512 K·kg/mol, molar mass of sucrose = 342 g/mol)

(b) If the boiling point of pure water at the location is 99°C (due to altitude), calculate the boiling point of the concentrated syrup.

(c) Explain why higher sugar concentration requires more energy for evaporation and how this affects production costs.