Answer: -
- 0.348°C is the melting point of a solution in which 2.5 grams of sodium chloride is added to 230 mL of water
Explanation: -
Mass of NaCl = 2.5 g
Molar mass of NaCl = 23 x 1 + 35.5 x 1 = 58.5 g / mol
Number of moles of NaCl = Mass of NaCl / Molar mass of NaCl
= 2.5 /58.5
= 0.043 mol
230mL of water has 0.043 mol.
1000mL of water has (0.043 mol x 1000 mL ) / 230mL
= 0.187 mol
Thus molality of NaCl =0.187 m
The molal freezing point depression constant of water = 1.86 °C/m
Depression in freezing point = 1.86 °C/m x 0.187 m
= 0.348°C
Melting point = 0 - 0.348°C
= - 0.348°C
