99 Percentile Qs Bank for JEE MainChemistrySolutions
What will be the molar mass of solute if vapour pressure of pure benzene is 450 ~mm Hg when 1 5 ~g of non volatile solute is added to 30 ~g of benzene? (Vapour pressure of solution =400 ~mm Hg , atomic mass C =12, H =1 )
Options
- A1.35 1 ~g ~mol ⁻¹
- B2.26 1 ~g ~mol ⁻¹
- CX ₃ .28 4 ~g ~mol ⁻¹
- D4. 30 0 ~g ~mol ⁻¹
Correct answer
A. 1.35 1 ~g ~mol ⁻¹
Step-by-step solution
P ⁰=450 ~mm ~Hg , P =400 ~mm ~Hg , M ₁=78 ~g ~mol ⁻¹ (molar mass of benzene), W ₁=30 ~g , ~W ₂=1.5 ~g , M ₂=? M ₂= W ₂ M ₁ ~W ₁ P ₀ ( P ₀- P ) M ₂= 1.5 78 30 450 (450-400) =35.1 ~g ~mol ⁻¹