Question

If α is the degree of dissociation of Na₂SO₄, the van’t Hoff factor (i) used for calculating the molecular mass is ______.

विकल्प

• 1 − 2α

• 1 + 2α

• 1 − α

• 1 + α

Answer 1

If α is the degree of dissociation of Na₂SO₄, the van’t Hoff factor (i) used for calculating the molecular mass is 1 + 2α.

Explanation:

When Na₂SO₄ dissociates in water.

\[\ce{Na2SO4 -> 2Na+ + SO^2−_4}\]

1 formula unit gives 3 ions (2 Na⁺ and \[\ce{SO^2−_4}\])

Let α be the degree of dissociation.

Van’t Hoff factor (i) = 1 + α(n − 1)

Where:

n = 3 (total ions from one unit)

α = degree of dissociation

So, i = 1 + 2α

This is the van’t Hoff factor used in calculating molecular mass for Na₂SO₄.