a. molality
b. molarity
c. mole fraction
20% mass/mass $\quad$ f = 1.202g/ml
20g $\quad$ K I(39.1 126q) = 1660g/mol
80g $\quad$ solvent water
$^nKI = \frac{20}{166}$ = 0.12moles
molality = $\frac {\text{moles of solvent}}{\text{water of solvent}}$
$= \frac {0.12}{80} \times 1000 = \frac {120}{80} = 1.5m$
molarity = $\frac {\text{moles of solute}}{\text{volume of solution}}$
= $\frac {0.12}{83.19} \times 1000 = 1.44$
V = $\frac {100g}{1.202g/ml} = 83.19ml$
$^XKI = \frac {4^nKI}{^nKI + ^nH_2O} = \frac {0.12}{0.12+ \frac {80}{18}} = 0.026$