Question

A solution of glucose(C6H12O6) is isotonic with of 4g urea(NH2CONH2)per litre of solution. The concentration of glucose is:

Answer 1

here the ans. is 1/15 molarity

Answer 2

Answer: Concentration of glucose is 0.07 M or 12 g/L

Explanation:

Isotonic solutions are those solutions which have the same osmotic pressure.  If osmotic pressures are equal at the same temperature, concentrations must also be equal.

$\pi =CRT$

Thus: $C_{urea}=C_{glucose}$ where concentration is in molarity.

$\pi$ = osmotic pressure

C= concentration in Molarity

R= solution constant

T= temperature

For the given solution: 4 g of urea $(NH_2CONH_2)$ is dissolved to make 1 L of solution.

$Molarity=\frac{\text{Mass of solute}}{\text{Molar mass of solute}\times \text{volume of solution in L}}$

$C_{urea}=\frac{4}{60\times 1L}=0.07moles/L$

As $C_{urea}=C_{glucose}$

$C_{glucose}=0.07mole/L=0.07mole/L\times 180g/mole=12g/L$

Thus concentration of glucose is 0.07 moles/L or 12 grams/L