Answer:
-4.59°C
Explanation:
Let's see the formula for freezing point depression.
ΔT = Kf . m . i
ΔT = Freezing T° of pure solvent - Freezing T° of solution
Kf = Freezing constant. For water if 1.86°C/m
m = molality (moles of solute in 1kg of solvent)
i = Van't Hoff factor.
0°C - Freezing T° of solution = 1.86°C /m . 1.30m . 1.9
Freezing T° of solution = - (1.86°C /m . 1.30m . 1.9)
Freezing T° of solution = - (1.86°C/m . 1.30m . 1.9) → -4.59°C
NaCl → Na⁺ + Cl⁻
