Question

a saline solution begins to freeze at -1.13 degrees. Express the concentration of NaCl in this solution in mass%. Kf for water is 1.86C degree/m.

Answer 1

The Percentage mass of NaCl is 1.78%.

What is the percent mass concentration of the NaCl in saline solution.

The percent mass concentration of NaCl in the saline solution is determined from the molality of the solution.

The molality of the solution is further obtained from the freezing point depression formula.

The freezing point depression formula is given as follows:

• ΔT = Kf * m * i

where;

• ΔT is the freezing point change
• Kf is a constant
• m is the molality of the solution
• i is the van't Hoff factor

For the solution of NaCl;

ΔT = 0 - (-1.13) = 1.13

Kf = 1.86 °/m

i = 2

m = ΔT/(Kf * i)

m = 1.13/(1.86 * 2)

m = 0.3038 mol/kg

molar mass of NaCl = 58.5 g/mol

Mass of NaCl = 0.3038 * 58.5 = 17.8 g in

Percentage mass of NaCl = (17.8/1000) * 100

Percentage mass of NaCl = 1.78%

In conclusion, the percent mass of NaCl is obtained from the molality of the solution.

Learn  more about molality and freezing point depression at: https://brainly.com/question/14116544

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