Question

Choose the correct formula(s) regarding Van't hoff factor $\left(i\right)$ :

• A. $i=\frac{\text{Normal molar mass}}{\text{Abnormal molar mass}}$
• B. $i=\frac{\text{Abnormal molar mass}}{\text{Normal molar mass}}$
• C. $i=\frac{\text{No. of moles before association/dissociation}}{\text{No. of moles after association/dissociation}}$
• D. Both (b) and (c).

Answer 1

The correct option is A $i=\frac{\text{Normal molar mass}}{\text{Abnormal molar mass}}$

Van't Hoff factor $\left(i\right)$: It is a correction factor by which actual extent of association/ dissociation can be expressed.
For electrolytic solute undergoing association :
$i<1$
For electrolytic solute undergoing dissociation :
$i>1$
For non-electrolytic solute:
$i=1$

$i=\frac{\text{Experimental Colligative Property (observed)}}{\text{Calculated Colligative Property (expected)}}$

$i=\frac{\text{No. of moles after association/dissociation}}{\text{No. of moles before association/dissociation}}$

$i=\frac{\text{Normal/Theoretical molar mass}}{\text{Abnormal/Observed molar mass}}$