Question

Calculate the number of moles of methyl alcohol of 2 Molal solution in 5 ${dm}^3$.The density of solution is 0.981 kg $d{m}^{-3}$. Given that, molar mass of methyl alcohol is 32 g $mo{l}^{-1}$.

Answer 1

Given,

$m=2$

$V=5d{m}^3$

$\rho =0.981kg/d{m}^3$

$M=32g/mol$

Since $m=\frac{1000M}{\rho \times 1000-M_b\times M}$

Since $2=\frac{1000M}{0.981\times 1000-32\times M}$

Hence, $M=1.842moles/d{m}^3$

Number of moles of methyl alcohol=$M\times V=1.842\times 5=9.21moles$