Question

Calculate
(a) molality
(b) molarity and
(c) mole fraction of $KI$ if the density of $20\%$ (mass/ mass) aqueous $KI$ is $1.202gm{L}^{-1}$

Answer 1

Molality
$\frac{w}{w}\%=20$
$100gm$ solution has $20gm$ KI
$80gm$ solvent has $20gm$ KI
$m=\frac{\frac{20}{166}}{\frac{80}{1000}}=1.51mol$
Molarity
Volume = $\frac{m}{d}\Rightarrow \frac{20}{1.2}=83.2$
Molalrity $=\frac{.120\times 1000}{83.2}$
$=1.44m$
Mole fraction $=\frac{\frac{20}{166}}{\frac{80}{18}+\frac{20}{166}}$