Between aqueous glucose and NaCl solutions of equal molality, if NaCl ionises completely, which solution will show a greater elevation in boiling point?
Answer and explanation
Correct answer: The NaCl solution
Boiling-point elevation is given by ΔTb = iKb m. The two solutions have the same solvent and molality, so Kb and m are identical. Glucose does not ionise and has i = 1, whereas completely ionised NaCl produces Na+ and Cl−, giving i approximately 2. Therefore NaCl produces nearly twice the elevation under the stated ideal assumption.
Frequently asked questions
What is the correct answer to this question?
The NaCl solution
Why is this the correct answer?
Boiling-point elevation is given by ΔTb = iKb m. The two solutions have the same solvent and molality, so Kb and m are identical. Glucose does not ionise and has i = 1, whereas completely ionised NaCl produces Na+ and Cl−, giving i approximately 2. Therefore NaCl produces nearly twice the elevation under the stated ideal assumption.
Which subject and chapter does this question cover?
This is a Class 12 Chemistry question. Chapter: Chapter 01: Solutions. Topic: 5: Colligative Properties.
