Q.

Mass of glucose (C6H12O6) required to be dissolved to prepare one litre of its solution which is isotonic with 15 g L-1 solution of urea (NH2CONH2) is

(Given: Molar mass in g mol-1 C : 12, H : 1, O : 16, N : 14)                      [2024]

1 55 g  
2 15 g  
3 30 g  
4 45 g  

Ans.

(4)

As the two solutions of glucose and urea are isotonic, it means they have the same osmotic pressure at a given temperature.

π1(Glucose)=π2(Urea)

C1RT=C2RT  (π=CRT)

n1V1RT=n2V2RT n1V1=n2V2 w1M1V1=w2M2V2

w1=15×18060=45 g

(Molar mass; glucose = 180 g mol-1, urea = 60 g mol-1)