Verified Answer :

Colligative
properties calculations are used for this type of problem. Calculations are as
follows:



ΔT(freezing point)  = (Kf)m

ΔT(freezing point)
= 1.86 °C kg / mol (0.50 mol/kg)

ΔT(freezing point)  = 0.93 °C

Tf - T = 0.93 °C
T = -0.93 °C

Answer:

The expected freezing point of a 0.50 m solution of sodium sulfate is -0.93°C.

Explanation:

\(\Delta T_f=K_f\times m\)

where,

\(\Delta T_f\) =depression in freezing point =

\(K_f\) = freezing point constant

m = molality

we have :

\(K_f\) =1.86°C/m ,

m = 0.50 m

\(\Delta T_f=1.86^oC\times 0.50 m\)

\(\Delta T_f=0.93^oC\)

Freezing point of pure water = T =  0°C

Freezing point of solution = \(T_f\)

\(\Delta T_f=T-T_f\)

\(T_f=T-\Delta T_f=0^oC-0.93^oC=-0.93^oC\)

The expected freezing point of a 0.50 m solution of sodium sulfate is -0.93°C.