Q. If $\alpha$ is the degree of dissociation of $Na_{2}SO_{4}$ the van’t Hoff factor (i) used for calculating the molecular mass is
A) $1 - 2\ \alpha$
B) $1 + 2\ \alpha$
C) $1 - \alpha$
D) $1 + \ \alpha$
Explanation
(b)
$\ \ \ \ \ \ \ Na_{2}SO_{4} \rightleftharpoons 2Na^{+} + SO_{4}^{2 -}$
van’t Hoff factor i=[1+(y-1)$\ \alpha$]
where y is the number of ions from one mole solute, (in this case =3), $\alpha$ the degree of dissociation.
i=(1+2$\ \alpha)$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.