PTP 4 - Notre dame Chemistry - Home



Pre-Test Assignment for Stoichiometry, Solutions & Reactions Test

1. Pure acetic acid is a liquid with a density of 1.049 g/mL at 250C. Calculate the molarity of a solution of acetic acid made by dissolving 20.00 mL of acetic acid at 250C in enough water to make 250.0 mL of solution.

2. A mixture contains 89.0% sodium chloride, 1.5% magnesium chloride, and 8.5% sodium sulfate by mass. What is the molarity of chloride ions in a solution formed by dissolving 7.50g of the mixture in enough water to form 500.0 mL of solution?

3. The hydrate MgNH4PO4• 6H20 has a solubility of 0.023g/100.mL in water. Suppose a 5.02 g sample were washed with 20.0 mL of water. What percent of the hydrate would be lost?

4. Describe how you would prepare the desired solution being specific with regards to lab equipment and numerical amounts.

250.0 mL of 1.0 M nitric acid. All you have available is a bottle of 6.0 M nitric acid.

5. A commercial bleaching solution contains 3.62 mass % sodium hypochlorite, NaOCl. What is the mass of sodium hypochlorite in a bottle containing 2.50 kg of bleaching solution?

6. The presence of the radioactive gas radon in well water obtained from aquifers that lie in rock deposits presents a possible health hazard in parts of the United States. A sample consisting of various gases contains 3.5 x 10-6 mole fraction of radon. This gas at a total pressure of 32 atm is shaken with water at 30.0 0C. Assume that the solubility of radon in water with 1 atm of the gas over the solution at 30.0 0C is 7.27 x 10-3 M. Calculate the molar concentration of radon in the water.

7. A 2.5 g sample of groundwater was found to contain 5.4 μg of Zn2+ ions. What is the concentration of zinc ions in parts per million?

8. Mr. Irvin needs to make some more salt solution for his Honors Biology Osmosis Lab.

He needs 400.0 mL of each of the following concentrations: 1.5%, 2.5%, 5.0%, 10.0%, and 20.0%. How many mL of a 20.0% stock solution should be made in order to have enough to make all of the solutions by means of dilution?

After doing the calculations, describe how to make the 1.5% solution.

Solution Multiple Choice

The following questions are worth one point each. Try to answer without a calculator. You can check yourself with a calculator.

9. The solubility of cadmium (II) chloride is 140 g per 100 mL of solution. What is the molar solubility of a saturated solution of cadmium(II) chloride?

a) 0.765 M

b) 1.31 M

c) 7.65 M

d) 12.61 M

e) 0.131 M

10. To make a solution, 3.45 mol of C6H13Cl and 1.26 mol of C5H12 are mixed. Which of the following is needed, but not readily available, to calculate the molarity of this solution?

a) the density of the solution

b) the densities of C6H13Cl and C5H12

c) the temperature

d) the molar masses of C6H13Cl and C5H12

e) the volumes of C6H13Cl and C5H12

11. A polluted pond contains 25 ppb of lead ions. What is the concentration of lead ions in molarity units?

a) 1.2 x 108 M

b) 1.2 x 10-7 M

c) 2.5 x 10-8 M

d) 0.121 M

e) 1.2 x 10-10 M

12. The solubility of acetylene gas, CHCH, in water at 300C is 0.975 g L-1 when the pressure of acetylene is 1.00 atm. What is the solubility, at the same temperature, when the pressure of acetylene above the water is reduced to 0.212 atm?

a) 4.60 g L-1

b) 0.207 g L-1

c) 0.975 g L-1

d) 0.212 g L-1

e) the answer cannot be determined from given data

13. If 20.0 g of ethanol (46 amu) and 30.0 g of water (18 amu) are mixed together, the mole fraction of ethanol in this mixture is

a) 0.207 b) 0.261 c) 0.739 d) 0.793 e) 4.83

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