Elevation Of Boiling Point
The molal elevation constant (Kb) of water is 0.52 K kg mol⁻¹. The boiling point elevation when 6.0 g of urea (molar mass = 60 g mol⁻¹) is dissolved in 500 g of water is:
Select the correct option:
Solution
0.104 K
Moles of urea = 6.0 / 60 = 0.1 mol. Mass of solvent = 500 g = 0.5 kg. Molality (m) = moles of solute / mass of solvent in kg = 0.1 / 0.5 = 0.2 mol kg⁻¹. Elevation of boiling point ΔTb = Kb × m = 0.52 × 0.2 = 0.104 K. Urea is a non-electrolyte, so the van't Hoff factor i = 1 and does not affect the calculation. The boiling point of water increases from 373.15 K to 373.254 K. This demonstrates that boiling point elevation is directly proportional to the molal concentration of solute particles.
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About This Question
- Subject
- chemistry
- Chapter
- solutions
- Topic
- elevation of boiling point
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
0.104 K
Moles of urea = 6.0 / 60 = 0.1 mol. Mass of solvent = 500 g = 0.5 kg. Molality (m) = moles of solute / mass of solvent in kg = 0.1 / 0.5 = 0.2 mol kg⁻¹. Elevation of boiling point ΔTb = Kb × m = 0.52 × 0.2 = 0.104 K. Urea is a non-electrolyte, so the van't Hoff factor i = 1 and does not affect the calculation. The boiling point of water increases from 373.15 K to 373.254 K. This demonstrates that boiling point elevation is directly proportional to the molal concentration of solute particles.
This easy difficulty chemistry question is from the chapter solutions, covering the topic of elevation of boiling point. It appeared in the 2025 exam.
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