Question

A compound $M{X}_2$ has observed and normal molar masses 65.6 and 164 respectively. The apparent degree of ionization of $M{X}_2$ is:

• A. $75\%$
• B. $85\%$
• C. $65\%$
• D. $25\%$

Answer 1

The correct option is A $75\%$

Observed molar mass $=65.6$

Normal molar mass $=164$
So, $i\times 65\cdot 6=164$;

$i=\frac{164}{65.6}=2.5$
And we know that, $i=1+\alpha (n-1)$
$n=3$, as one $M^{+}$ and two $X^{-1}$ are present.
Therefore, $2.5=1+\alpha (3-1)$
$\alpha =\frac{1.5}{2}$
$\alpha =0.75$
$\alpha \%=0.75\times 100=75\%$

Hence, the correct option is $A$