Compositions of solutions

1. How many grams of calcium nitrate and water are in 130 g of a 20% solution?

Solution:

100 grams of solution ........... 20 g of nitrate

130 g ......................................... x g of nitrate

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The mass of water is calculated as 130 − 26 = 104 g of water. The solution consists of 26 grams of calcium nitrate and 104 grams of water.

2. In 100 ml of water, 30 g of blue vitriol (copper(II) sulfate pentahydrate) were dissolved. What is the mass concentration of the solution thus prepared?

Solution:

First, it is necessary to calculate the amount of pure sulfate in blue vitriol.

M(CuSO4·5H2O) = 249.68 g·mol-1

M(CuSO4) = 159.60 g·mol-1 

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The mass of the solution is 100 g (water) + 30 g (blue vitriol) = 130 g. The concentration of the solution is therefore:

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3. How many grams of sodium hydroxide are needed to prepare 5 liters of a 10% solution with density ρ = 1115 kg·m-3?

Solution:

We will use a combination of the formula for mass concentration and density:

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where m´ is the mass of the solution, V´ is the volume of the solution, and ρ´ is the density of the solution.

After substituting numerical values:

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To prepare 5 liters of a 10% solution, we need 557.5 g of NaOH.

4. Calculate the molar concentration of a 22% sulfuric acid solution with density 1.1548 g·cm-3.

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5. An aqueous ethanol solution contains 90 ml of pure alcohol in 150 ml of solution. What is the volume percent and mass percent of the solution?

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6. How many grams of potassium chloride and how many milliliters of water are needed to prepare 245 g of a 2.5% solution?

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7. What is the mass of potassium permanganate present in 25 ml of a 0.02 molar solution?
M(KMnO4) = 158.342 g·mol-1.

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8.

What amount concentration will a solution of ammonium iron(III) sulfate have if 1 ml of such a solution corresponds to 1 mg of Fe2O3? M(Fe2O3) = 159.7 g·mol-1.

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9. What is the mass fraction and percent composition of a solution that contains, in 10 ml of water, 1.02 of dissolved substance?

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10. What are the amount concentration and mass concentration of a nitric acid solution with a mass percent of 40? ρ40 = 1.252 g·cm-3, Mr(HNO3) = 63.01.

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