Question

$A\,\,0.5\,\,g/L$ solution of glucose is found to be isotonic with a $2.5\,\,g/L$ solution of an organic compound. What will be the molecular weight of that organic compound?

• A. $300$
• B. $600$
• C. $900$
• D. $200$

Answer 1

Answer: (C)

$900$

Answer 2

Molarity of glucose solution $=\frac{0.5\,\,g}{180\times 1L}=0.00277\,\,M$ Isotonic solution have equal molar concentrations, hence molarity of organic compound solution $=0.00277\,\,M$ $\therefore$ Molecular weight of compound $=\frac{2.5}{0.00277\times 1}=900$