General Chemistry



General Chemistry Unit 7 Solutions

1. Problems - Making Solutions and Dilution

1. Find the concentration of the solute in terms of molarity for each of the following solutions:

a) 1.2 moles of HCl in 2 liters of solution

b) 95 grams of SrSO4 in 1.7 liters of solution

c) 35 grams of CuSO4 in 1250 mL of solution

2. Determine the amount of solute (in grams) needed to make each of the following solutions:

a) 1.00 L of 1.0 M NaCl

b) 100. mL of 0.25 M K2SO4

3. Determine how much of the given stock solution is needed to make the desired solution:

a) 25.00 mL of 0.25 M NaCl from 1.0 M NaCl stock solution

b) 100. mL of 0.100 M HCl from concentrated HCl with a molarity of 12.0 M

c) 50.00 mL of 0.015 M MgSO4 from 0.55 M MgSO4 stock solution

4. In the reaction,

AlCl3(aq) + 3AgNO3(aq) ( 3AgCl(s) + Al(NO3)3(aq).

How many grams of AgCl are produced when 42.0 g of AlCl3 reacts with an excess of AgNO3?

2. Problems - More Solutions and Dilutions

1. What is the molarity of the solution produced when 145 g of sodium chloride is dissolved in sufficient water to prepare 2.75 L of solution?

2. How many grams of potassium chloride are needed to prepare 750 mL of a 1.5 M solution of potassium chloride in water?

3. To prepare 0.500 L of a 2.50 M solution of potassium hydroxide (KOH), how many grams of potassium hydroxide must be used?

4. Briefly describe how you would go about making the solution above (in #3).

5. What is the molarity of 500. mL of solution containing 95.2 g of magnesium chloride?

6. How much stock solution must be diluted in order to make 100. mL of 0.10 M HCl. The stock solution is 6.0 M.

7. You have a stock solution of 2.0 M NaOH. How much of the stock solution would you need to dilute to make 250. mL of a 0.5 M solution?

8. Briefly describe how you would go about making the dilution above (in # 7).

9. Determine the number of molecules of C2H4O2 in 35.44 g of C2H4O2.

3. Problems – Solubility and Solubility Curves

Use table E to answer the questions below:

1. Which aluminum-containing compound will decompose when placed in water?

2. How would you describe the solubility of Hg2Br2?

3. Rank the following substances in order of increasing solubility: ammonium nitrate, zinc carbonate, calcium hydroxide.

4. Of the following substances, which substance(s) would not make a concentrated solution(s)?

(NH4)2SO4 AlCl3 BaBr2 Ag2SO4 Ca3(PO4)2

5. What three cations will always make concentrated solutions, regardless of the anion in the compound? What anion will always make concentrated solutions, regardless of the cation in the compound?

|[pic] |

The graph above is similar to Table D in

your Reference Tables. Use it to answer questions 6 - 18 below.

6. Which compound, NaClO3 or Ce2(SO4)3, is more soluble in water? Explain how you know:

7. Classify each of the following solutions as unsaturated (u), saturated (s), or supersaturated (s).

a) 90 g of NaClO3 in 100 g H2O at 10 °C

b) 125 g of NaClO3 in 100 g H2O at 30 °C

c) 25 g of NaClO3 in 100 g H2O at 140 °C

8. Classify each of the following solutions as unsaturated, saturated, or supersaturated.

a) 10 g of Ce2(SO4)3 in 100 g H2O at 25 °C

b) 5 g of Ce2(SO4)3 in 50 g H2O at 25 °

9. Find a point on the graph that would represent an unsaturated solution of Ce2(SO4)3. Put a dot there and label the point “A”. Find a point on the graph that would represent a saturated solution of Ce2(SO4)3. Put a dot there and label the point “B”. Find a point on the graph that would represent a supersaturated solution of Ce2(SO4)3. Put a dot there and label the point “C”.

10 Study the shape of the curve representing NaClO3. Describe the slope:. Based on this slope, determine if NaClO3 dissolving in water is an endothermic or exothermic process. Explain.

11. Study the shape of the curve representing Ce2(SO4)3. Describe the slope:

12. Based on this slope, determine if Ce2(SO4)3 dissolving in water is an endothermic or exothermic process. Explain. water at 50 °C to make a saturated solution? How much NaClO3 will dissolve in 50 g of water at 25 °C to make a saturated solution? How many grams of NaClO3 are needed to saturate 100 g of H2O at 45 °C?

13. How many grams of Ce2(SO4)3 are needed to saturate 100 g of H2O at 90 °C?

14. At 20 °C a saturated solution of sodium chlorate contains 100 g of solute in 100 g of water. How many grams of sodium must be added to saturate the solution if the temperature is raised to 50 °C?

15. A saturated solution of Ce2(SO4)3 is prepared by dissolving 10 g of Ce2(SO4)3 in 100 g of water at 25 °C. Describe the solution once its temperature is raised to 100 °C.

16. A solution containing 100 g of NaClO3 at 100 °C is cooled quickly to 0 °C. Would you expect to see a precipitate form? Describe the solution if a precipitate does not form.

17. A solution containing 10 g of Ce2(SO4)3 at 15 °C is heated to 60 °C. Would you expect a precipitate to form at the higher temperature? Why or why not?

18. Describe the solution if a precipitate does not form.

4. Solubility Curves (I used these questions to make Solubility Reading & Practice kl)

Use the graph of solubility versus temperature (Table D) to answer the questions below.

1. How many grams of NaNO3 are needed to saturate 100 mL of H2O at 20º C?

2. How many grams of NaNO3 are needed to saturate 50 mL of H2O at 45º C?

3. Classify each of the following solutions as unsaturated, saturated, or supersaturated.

a) 75 g NaNO3 in 100 mL at 10º C

b) 120 g NaNO3 in 100 mL at 50º C

c) 100 g NaNO3 in 100 mL at 40º C

d) 110 g NaNO3 in 100 mL at 45º C

4. HCl, NH3, and SO2 are gases at the temperature range shown in the solubility graph above. How are the solubilities of these gases different from the solubility of all the other compounds on the graph? Explain this difference.

5. What substance shown on the graph is most soluble at 10º C?

6. What substance is least soluble at 70º C?

7. What ionic substance is least soluble at 70º C?

8. An aqueous solution of potassium chlorate at 100º C made from 55 g of KClO3 in 100 g of water is cooled suddenly to 25º C. How many grams of precipitate will form?

9. 50 g of KCl is dissolved in 100 g of H2O at 75º C. The solution is heated to 85º C. Is the warmer solution saturated, unsaturated, or supersaturated? Explain how you know.

10. Write the name and chemical formula for each of the substances shown on the solubility graph.

5. Mixed Review Problems

1. How many grams of Pb(NO3)2 are in 145 mL of 0.500 M Pb(NO3)2?

2. How many molecules of C6H12O6 are in 252 mL of 1.50 M C6H12O6 solution?

3. In the reaction,

H2SO4(aq) + 2NaOH(aq) ( 2H2O(l) + Na2SO4(aq),

100. grams of H2SO4 is mixed with 100. grams of NaOH. Determine the limiting reagent and the mass of Na2SO4 produced.

4. If 3.50 ( 1023 molecules of C3H7OH are used to make 600. mL of solution, determine the molarity of that solution.

5. Using table D,

a) How many grams of KNO3 are needed to saturate 100. mL of H2O at 20º C?

b) How many grams of NaNO3 are needed to saturate 50 mL of H2O at 50º C?

6. Describe how one should make 100. mL of 2.0 M NaCl solution.

7. Consider the reaction.

HCl(aq) + Na2CO3(s)( 2NaCl(aq) + H2O(l) + CO2(g),

How many liter of CO2(g) at STP are produced when 55.0 mL of 1.00 M HCl is mixed with an excess of Na2CO3(s)?

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