Question

$40$g MgO dissolves in $H_{2}O$ to form $200$ ml of solution, if density of solution is $1.5$g/ml. Calculate Mole fractions of solute and solvents.

Answer 1

MgO is solute & $H_{2}O$ is solvent weight of solvte $\left(W_A\right)=40g$

Density of solution $=1.5g/ml$ volume of solution $=200mL$

$\therefore$ weight of solution = Density $\times$ volume

$=1.5\times 200$

$=300g$

Weight of solvent $\left(W_B\right)=$ wt of $so{l}^n$ -wt of. solute

$=300-40=260$

$n_A=\frac{weightofsolute}{molecularweightofsolute}$ $n_B=\frac{weightofsolvent}{molecularwtofsolvent}$

$n_A=\frac{40}{40}=1$ $n_B=\frac{260}{18}=14.44$

$x_A=\frac{n_A}{n_A+n_B}$ $x_B=\frac{n_B}{n_A+n_B}$

$=\frac{1}{1+14.44}$ $=\frac{14.44}{1+14.44}$

$x_A=0.0647$ $x_B=0.9353$