Concentrations: molality and molar fraction

Tutorial 1

    

Use this schematic "lattice" and →    définitions 1 or →    définitions 2 to resolve the following exercise:

Exercise $ 3\; kg$ of an aqueous ammonia solution contain $ 170 \;g $ of $NH_3$ . Calculate the molality of $NH_3$ ! Solution (Click): Scheme and formulas: .......... Calculation: ..........$n_{so}=\frac{m_{so}}{M{so}} $ $=$ $\frac{170}{17,0}=10\;mol$
$m_{sl}$ $=$ $3000-170=2830\;g$
$\mu_{so}$ = $\frac{n_{so}}{m{sl}}=\frac{10}{2,83}$=$3,53 \frac{mol}{kg}$