Question

$22.22$ gram of urea was dissolved in $300$ grams of water. Calculate the number of moles of urea and molality of the urea solution.
(Given: Molar mass of urea $=60$ gram $mo{l}^{-1}$).

Answer 1

$\text{Number of moles of urea}=\frac{\text{Mass}}{\text{Molar mass}}=\frac{\text{22.22 g}}{\text{60 g/mol}}=\text{0.37 mol}$

$\text{Mass of water}=\text{300 g}\times \frac{\text{1 kg}}{\text{1000 g}}=\text{0.300 kg}$
$\text{Molality m}=\frac{\text{Number of moles of urea}}{\text{mass of water (in kg)}}=\frac{\text{0.37 mol}}{\text{0.300 kg}}=\text{1.23 mol/kg}$