Calculate mass percent, mole fraction, molarity and molality?

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A solution was prepared by dissolving 39.0g of KCL in 225g of water.

1. Calculate the mass percent of KCl in the solution.

2. Calculate the mole fraction of KCl in the solution.

3. Calculate the molarity of KCl in the solution if the total volume of the solution is 239mL .

4. Calculate the molality of KCl in the solution.

• 1. % = (39.0 / 39.0 + 225 ) x 100 = 14.8 %

2.

Molecular weight KCl = 74.55 g/mol

39.0 / 74.55 = 0.523 moles KCl

Molecular weight H2O = 18 g/mol

225 / 18 = 12.5 moles H2O

X (KCl) = 0.523 / 0.523 + 12.5 = 0.0401

3.

V = 0.239 L

M = 0.523 / 0.239 = 2.19

4.

m = 0.523 /0.225 Kg = 2.32

• A solution was prepared by dissolving 23.0g of KCL in 225g of water.

The measures are different.

1. Calculate the mass percent of KCl in the solution.

2. Calculate the mole fraction of KCl in the solution.

3. Calculate the molarity of KCl in the solution if the total volume of the solution is 239mL .

4. Calculate the molality of KCl in the solution.

1) 9.27%

2) 2.41 x 10^-2

3) 1.29 M

4) 1.37 m

I used Dr. A’s steps to get the answer for the changed measurement.

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• 1=17%

2=5.3%

3=10%

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