What is the melting point of a solution in which 2.5 grams of sodium chloride is added to 230 ml of water

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- 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