Q. A solution containing 10 g per dm³ of urea (molecular mass = 60 g mol⁻¹) is isotonic with a 5% solution of a non-volatile solute. The molecular mass of this non-volatile solute is :
A) 200 g mol⁻¹
B) 300 g mol⁻¹
C) 400 g mol⁻¹
D) 500 g mol⁻¹
Explanation
[Solution from source] Isotonic solutions of non-electrolytes have equal molar concentrations. Urea: 10 g/L ÷ 60 = 1/6 mol/L. A 5% solution has 50 g/L (taking 5 g per 100 mL), so 50/M = 1/6 and M = 300 g mol⁻¹. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.