1. An aqueous solution of aluminum nitrite is prepared by dissolving 6.93 g of a

Question

1. An aqueous solution of aluminum nitrite is prepared by dissolving 6.93 g of aluminum nitrite in 9.60×102 g of water. The density of the solution is 1.21 g mL-1.
a) Determine the mass percent of aluminum nitrite in the solution.

b) Determine the mole fraction of aluminum nitrite in the solution.

2. An aqueous solution of potassium acetate is prepared by dissolving 1.82 g of potassium acetate in 4.34×102 g of water. The density of the solution is 1.20 g mL-1.
Determine the molarity (in mol/L) of potassium acetate in the solution.

Explanation / Answer

Given,

Mass of aluminium nitrite = 6.93 g

Mass of water = 9.6 x 10^2 = 960 g

Total Mass = 6.93 + 960 = 966.93 g

a) Mass Percent of aluminium nitrite = (6.93 / 966.93) x 100 = 0.717 %

Molar Mass of Aluminium Nitrite = 165

Moles of Aluminium Nitrite = 6.93 / 165 = 0.042 moles

Molar Mass of water = 18

Moles of Water = 960 / 18 = 53.33

Total number of moles = 53.33 + 0.042 = 53.375

b) Mole fraction of Aluminium Nitrite = 0.042 / 53.375 = 7.87 x 10^-4

2)

Given,

Mass of potassium acetate = 1.82 g

Molar mass of potassium acetate = 98.15

=> Moles of potassium acetate = 1.82 / 98.15 = 0.0185 moles

Mass of water = 434 g

Total Mass of solution = 434 + 1.82 = 435.82 g

Given, density of solution = 1.2 g / mL

=> Volume of solution = 435.82 / 1.2 = 363.18 mL = 0.36318 L

Molarity = Moles of potassium acetate / Volume of solution (in L)

=> Molarity = 0.0185 / 0.36318 = 0.051 mol / L

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