Question

Which has the lowest boiling point at 1 atm pressure?
(a) 0.1 M KCl
(b) 0.1 M Urea
(c) 0.1 M CaCl2
(d) 0.1 M A1Cl3

Answer 1

Answer:

0.1 M Urea has lowest boiling point

Explanation:

Answer 2

The lowest boiling point at 1 atm is option (b) 0.1M urea.

• On adding non-volatile solute to a solution, solute occupies the vacant spaces inside the solution and there is an increase in elevation in boiling point.
• Elevation in boiling point is calculated by the formula ikbm. here, kb is the ebullioscopy constant, i is the Vant's Hoff factor and m is the molality constant.
• i is equal to a number of molecules associated or dissociated from the total number of molecules present initially.
• As molality is the same in all three and kb is constant so, we will use i for determining the least boiling point substance.
• Urea does not dissociate so value of i here is 1 and in KCl it is 2 in CaCl2 it is 3 and in AlCl3 it is 4.
• So, AlCl3 has the highest boiling point and urea has the least.