Question

1.5% glucose (mol. wt. =180) solution is isotonic with 7.65 g/L glycerine solution. Find out mol. wt. of glycerine.

Answer 1

Isotonic solutions are two solutions which have same concentration.

$⟹$ Molarity of glucose $=\frac{15g}{180}\times \frac{1000}{1000}=\frac{1}{12}M$

$⟹$ Molarity of glycerine $=\frac{7.65g}{M}\times \frac{1000}{1000}=\frac{7.65}{M}$

$⟹\frac{1}{12}=\frac{7.65}{M}⟹M=7.65\times 12=91.8g$