Answer
See the answer below.
Work Step by Step
In 1 kg of each solution:
$n_{NaCl}=(5/100\times1000\ g)\div58.44\ g/mol=0.86\ mol\rightarrow m_{NaCl}=0.86\ mol/0.95\ kg=0.905\ m$
$n_{Na_2SO_4}=(5/100\times1000\ g)\div142.04\ g/mol=0.35\ mol\rightarrow m_{Na_2SO_4}=0.35\ mol/0.95\ kg=0.368\ m$
F.p. depression:
$\Delta T_f=iK_fm$
$i_{NaCl}=-3.05^{\circ}C/m\div(-1.86^{\circ}C/m\times 0.905\ m)=1.81$
$i_{Na_2SO_4}=-1.36^{\circ}C/m\div(-1.86^{\circ}C/m\times 0.368\ m)=1.99$
Yes, in both cases the trend of a decrease in the van't Hoff factor with the increase in weight percent of the solute is observed.
