Molality and mole fraction

Exercise 4

    

We have a $0.1\;m$ ($m$ = molal) solution of $NaOH$ in ethanol $C_2H_6O$ . What is the mole fraction of $NaOH $?

$1000\;g$ ethanol contain $0.1\;mol\;NaOH$ $n_{C_2H_6O}$ $=$ $\frac{m_{C_2H_6O}}{M_{C_2H_6O}}$ $=$ $21.74\;mol$ $X_{NaOH}$ $=$ $\frac{n_{NaOH}}{n_{C_2H_6O}+n_{NaOH}}$ $=$ $4.58\cdot 10^{-3}$