What is the expected freezing point of a 0.50 m solution of na2so4 in water kf for water is 1.86°c/m?
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.