molecular_masses

Q1

In certain solvent, phenol dimerises to the extent of 60%. Its observed molecular mass in the solvent should be

Ans:

i = 1 –

∴ 0.7

Observed =

Q2

A solution containing 8.6 g urea in one litre was found to be isotonic with a 5% (wt./vol.) solution of an organic non – volatile solute. The molecular weight of latter is

Ans:

For isotonic solution

⇒ M = 348.9

Q3

Osmotic pressure of blood is 7.55 atm at 310 K. An aqueous solution of glucose that will be isotonic with blood is...........wt/vol

Ans:

For isotonic solution p₁ = p₂

7.65 =

times; 0.0821 × 310

7.65 =

× 0.0821 × 310

= 54.1 g/lt = 5.41%M

Q4

The relationship between the values of osmotic pressures of 0.1 M solutions of KN0₃(P₁) and CH₃COOH (P₂) is

Ans:

For equimolar solution, osmotic pressure depends on the value of Vant Hoff s factor (i)

∴ Osmotic pressure ∴ i

KNO₃, being strong electrolyte, completing ionizes, i₁ = 2

But for CH₃COOH, i₂ = 1 + ∝

∴ i₁ > i₂ But P₁ < i₁

P₂ < i₂

∴ P₁ > P₂

Q5

The mol. weight of NaCl determined by studying freezing point depression of its 0.5% aqueous solution is 30. The apparent degree of dissociation of NaCl is

Ans:

⇒ α = 0.95.