UNIT 8 EXTRA PROBLEMS FOR THE WEB PAGE: Solutions

1. Calculate the molarity of a solution containing 10.0 g of sulfuric acid in 500. mL of solution. [0.204 M]

2. Calculate the mass in grams of sulfuric acid in 2.00 L of a 0.100 M solution. [19.6 g]

3. Each liter of human blood contains about 3.4 g of Na+ ions . What is the molarity of the Na+ in human blood serum? [0.15 M]

4. What mass of calcium bromide, CaBr2, is needed to prepare 150. mL of a 3.5 M solution? [105.32 g]

5. A chemist wants to dilute 50. mL of 3.50 M sulfuric acid to 2.00 M sulfuric acid. To what volume must it be diluted? [87.5 mL]

6. What will be the final concentration of a solution of 50. mL of 0.5 M H2SO4 added to 75 mL of 0.25M H2SO4. [0.35 M]

7. 2.3 g of ethanol (C2H5OH) is added to 500. g of water. Determine the molality of the resulting solution. [0.1 m]

8. What is the molality of a solution in which 49 g of sulfuric acid is dissolved in 250. g of water? [2.0 m]

9. Determine the mass of water to which 293 g of NaCl is added to obtain a 0.25 molal solution. [20. kg water]

10. By how much will 50. g of water have its freezing point depressed if you add 30. g of glucose (molar mass 180 g/mol) to it? [6.20C]

11. What is the freezing point of a solution of 92 g of alcohol (C2H5OH) and 500 g of H2O? [-7.440C]

12. What is the boiling point at standard pressure of a solution prepared by dissolving 234 g of NaCl in 500. g of water? [108.320C]

The following problems are for Honors only:

1. A wine has an acetic acid (CH3COOH) content of 0.66% by mass. If the density of the wine is 1.11 g/mL, what is the molarity of the acid? [0.12 M]

2. A student has 50.00 mg crystal of Ba(OH)2.8H2O and wants to make a solution of 0.12 M OH-. How much water must the student add to obtain such a solution? [2.65 mL]

3. If 25 mL of 0.11 M sucrose is added to 10. mL of 0.52 M sucrose, what would be the resulting molarity? [0.23 M]

4. A chemist discovered a new compound and wished to determine its molecular mass. She placed 2.00 g of the unknown compound in 10. g of water and found that the freezing point of the water was depressed to -1.220C. What is the molecular mass of the new compound? [305 g/mol]

5. Ethanol boils at 78.50C. If 10. g of sucrose (C12H22O11] is dissolved in 150 g of ethanol, at what temperature will the solution boil? Assume Kb = 1.200C/m. [78.730C]

The following is an example of an Honors test for the Solutions unit:

Multiple Choice:

1. Compared to pure water at standard pressure, a 1.0 molal sugar solution will have a:

(a) lower vapor pressure and lower boiling point (b) higher vapor pressure and higher boiling point (c) lower vapor pressure and higher boiling point (d) higher vapor pressure and lower boiling point

2. As the temperature increases, the solubility of most gases in water: (a) increases (b) decreases (c) remains the same

3. In questions 3-5, choose the letter of the VALID explanation for each of the observations.

EXPLANATIONS:

OBSERVATIONS:

3. More sugar dissolves in hot tea than in iced tea

4. Paint must be stirred before use

5. The path of a laser beam is not visible through pure water but can be clearly seen when a small amount of powdered milk is added to the water

6. What is the molarity of a solution that contains 4.0 g of NaOH in 500. mL of solution?

(a) 0.50 M (b) 0.10 M (c) 8.0 M (d) 0.20 M

7. What is the total number of chloride ions in 500. mL of 1.00 M MgCl2 solution?

(a) 3.0 x 1023 (b) 1.0 x 1023 (c) 6.0 x 1023 (d) 2.0 x 1024

8. The solubility of solids depends upon all of the following factors except:

(a) temperature (b) pressure (c) the nature of the solute (d) the nature of the solvent

9. A solution containing 10 g KNO3 per 100 g H2O at 20oC is considered to be:

(a) dilute and unsaturated (b) dilute and supersaturated (c) concentrated and unsaturated (d) concentrated and supersaturated

10. To increases the solubility of a gas at constant temperature from 0.60 g/mL at 1.0 atm to 4.8 g/mL, the pressure would have to be increased to:

(a) 0.125 atm (b) 4.80 atm (c) 8.0 atm (d) 2.7 atm

11. What is the percent (m/v) of 500. mL of a solution that contains 60.0 g of potassium bromide?

(a) 8.33 % (b) 30.% (c) 12% (d) 60.%

12. Which solution contains the least grams of solute?

(a) 1 m NaCl (b) 2 m NH3 (c) 1 M KCl (d) 2 M HCl

13. How many mL of alcohol are present in 250 mL of 80% (v/v) alcohol solution?

(a) 200 mL (b) 250 mL (c) 80 mL (d) 160 mL

14. If one mole of each of the following solutes is added to the same amount of water, which solution has the highest boiling point?

(a) glucose, C6H12O6 (b) sodium hydroxide, NaOH (c) magnesium acetate, Mg(CH3COO)2 (d) copper(I) chloride, CuCl.

15. Which of the following is not a colligative property of a solution?

(a) density (b) boiling point elevation (c) freezing point depression (d) vapor pressure lowering

16. What mass of sucrose (C12H22O11) is needed to make 500 mL of a 0.10 M solution?

(a) 34.2 g (b) 100 g (c) 17.1 g (d) 68.4 g

17. To 400 mL of a 0.60 M solution of KI, a student adds enough water to make 1.0 L of a more dilute solution. What is the molarity of this new solution?

(a) 0.60 M (b) 0.24 M (c) 0.35 M (d) 0.18 M

18. 100 g of water contains 60.0 g of dissolved ammonium chloride at 60oC. This solution is:

(a) saturated (b) supersaturated (c) unsaturated

19. What is the molality of a solution that contains 4.9 g of H2SO4 dissolved in 5000 g of water?

(a) 0.01 m (b) 0.05 m (c) 0.20 m (d) 2.5 x 10-4 m

20. A water sample contains 0.60% (m/m) lead. What is the concentration of lead in ppm?

(a) 0.60 ppm (b) 60 ppm (c) 600 ppm (d) 6000 ppm

Problems:

21. Calculate the grams of salt in 400.0 mL of a 30.0% (by mass) solution if the density of the solution is 1.20 g/mL.

22. What will be the freezing point of an aqueous solution containg 52.8 g of ammonium sulfate in 200.0 g of water?

23. What is the molecular mass of a nondissociating compound if 3.84 g of the compound in 500.0 g of benzene gives a freezing point of 5.193oC? The normal freezing point of benzene is 5.500oC. For benzene, Kf = 5.12 oC/m.

24. 200. mL of 0.150 M Pb(NO3)2 are added to 30.0 mL of 0.200 M KCl solution. Write a balanced net ionic equation for the reaction and determine the grams of precipitate formed, assuming the reaction goes to completion.

25. Explain how you would prepare 100.0 mL of a 0.20 M solution of KI.

Answers: 1 c, 2 b, 3 c, 4 d, 5 b, 6 d, 7 c, 8 b, 9 a, 10 c, 11 c, 12 b, 13 a, 14 c, 15 a, 16 c, 17 b, 18 b, 19 a, 20 d.

21) 144 g ; 22) -11.2oC ; 23) 128 g/mol ; 24) 0.83 g ; 25) weigh out 3.32 g KI and make up the volume to 100.0 mL