A solution of urea (molar mass 56 g mol–1) boils at 100.18 ºC at atmospheric pressure. If Kf and Kb for water are 1.86 and 0.512 K kg mol–1 respectively, the above solution will freeze at:
1. –6.54 ºC
2. –0.654 ºC
3. 6.54 ºC
4. 0.654 ºC
The boiling point of benzene is 353.23 K. When 1.80 g of a non-volatile solute was dissolved in 90 g of benzene, the boiling point is raised to 354.11 K. The molar mass of the solute is:
Kb for benzene is 2.53 K kg mol–1
1. 55 g mol–1
2. 64 g mol–1
3. 58 g mol–1
4. 68 g mol–1