Question

A solution was prepared by dissolving 28.0g of KCL in 225g of water. Part A Calculate the mass percent ofKCL in the solution. Part B Calculate the mole fraction of KCL in the solution. Express the concentration numerically as a mole fraction in decimal form. Part C Calculate the molarity of in the solution if the total volume of the solution is 239 . Express your answer with the appropriate units. Part D Calculate the molality of KCL in the solution. Express your answer with the appropriate units.

Answer 1

Answer:

A. 11.1%

B. 0.0291

C. 1.57 M

D. 1.67 m

Explanation:

A.

Mass of KCl (solute): 28.0 g

Mass of water (solvent): 225 g

Mass of solution: 28.0 g + 225 g = 253 g

The mass percent of KCl is:

%KCl = (mass of KCl/mass of solution) × 100%

%KCl = (28.0 g/253 g) × 100%

%KCl = 11.1%

B.

The molar mass of KCl is 74.55 g/mol. The moles of KCl are:

28.0 g × (1 mol/74.55 g) = 0.376 mol

The molar mass of water is 18.02 g/mol. The moles of water are:

225 g × (1 mol/18.02 g) = 12.5 mol

The total number of moles is 0.376 mol + 12.5 mol = 12.9 mol.

The mole fraction of KCl is:

X(KCl) = moles of KCl / total moles

X(KCl) = 0.376 mol / 12.9 mol

X(KCl) = 0.0291

C.

The volume of the solution is 239 mL (0.239 L).

The molarity of KCl is:

M = moles of KCl / liters of solution

M = 0.376 mol / 0.239 L

M = 1.57 M

D.

The molality of KCl is:

m = moles of KCl / kilograms of solvent

m = 0.376 mol / 0.225 kg

m = 1.67 m