If α is the degree of dissociation of Na_{2}SO_{4}, the vant Hoff’s factor (i) used for calculating the molecular mass is

- 1 + 2α
- 1 - α
- 1 + α
- 1 - 2α

**Answer**

Na_{2}SO_{4} ↔ 2Na^{+} + SO_{4}^{2–}

1 0 0

1 – α 2α α

Vant Hoff factor (i) = (1 – α + 2α + α)/1

= 1 + 2α

**The correct option is A.**