AP Chemistry Name:
Chapter 4 Review Questions Period:
Discussion Questions:
4.1. Assume you have a highly magnified view of a solution of HCl that allows you to “see” the HCl. Draw this magnified view. If you dropped in a piece of magnesium, the magnesium would disappear and hydrogen gas would be released. Represent this change using symbols for the elements, and write out the balanced equation.
4.2. You have a solution of table salt in water. What happens to the salt concentration (increases, decreases, or stays the same as the solution boils? Draw pictures to explain your answer.
4.3. Order the following molecules from lowest to highest oxidation state of the nitrogen atom: HNO3, NH4Cl, N2O, NO2, NaNO2.
Questions:
4.4. Distinguish between the terms slightly soluble and weak electrolyte.
Exercises:
Aqueous Solutions: Strong and Weak Electrolytes
4.1. Show how each of the following strong electrolytes “breaks up” into component ions upon dissolving in water by drawing molecular-level pictures.
a. NaBr → Na+ + Br-
b. MgCl2 → Mg2+ + 2Cl-
c. Al(NO3)3 → Al3+ + 3NO3-
d. (NH4)2SO4 → 2NH4+ + SO42-
e. NaOH → Na+ + OH-
f. FeSO4 → Fe2+ + SO42-
g. KMnO4 → K+ + MnO4-
h. HClO4 → H+ + ClO4-
i. NH4C2H3O2 (ammonium acetate) → NH4+ + C2H3O4-
Solution Concentration: Molarity
4.2. A solution of ethanol (C2H5OH) in water is prepared by dissolving 75.0 mL of ethanol (density= 0.79 g/cm3) in enough water to make 250.0 mL of solution. What is the molarity of the ethanol in this solution? 5.2 M
4.3. Calculate the concentration of all ions present in each of the following solutions of strong electrolytes.
a. 0.15 M CaCl2 0.15M Ca2+ 0.30M Cl-
b. 0.26 M Al(NO3)3 0.26M Al3+ 0.78M NO3-
c. 0.25 M K2Cr2O7 0.50M k+ 0.25MCr2O72-
d. 2.0 x 10-3 M Al2(SO4)3 4.0x10-3M Al3+ 6.0x10-3M SO42-
4.4. What volume of a 0.100 M solution of NaHCO3 contains 0.350 g of NaHCO3?
41.7 mL
4.5. Describe how you would prepare 2.00 L of each of the following solutions?
a. 0.250 M NaOH from solid NaOH 20.0 g NaOH
b. 0.250 M NaOH from 1.00 M NaOH stock solution 500 mL NaOH
c. 0.100 M K2CrO4 from solid K2CrO4 38.8 g K2CrO4
d. 0.100 M K2CrO4 from 1.75 M K2CrO4 stock solution 114 mL K2CrO4
4.6. A standard solution is prepared for the analysis of fluoxymesterone (C20H29FO3), an anabolic steroid. A stock solution is first prepared by dissolving 10.0 mg of fluoxymesterone in enough water to give a total volume of 500.0 mL. A 100.0 μL aliquot (portion) of this solution is diluted to a final volume of 100.0 mL. Calculate the concentration of the final solution in terms of molarity. 5.94x10-8M
4.7. Write the balanced molecular equation, complete ionic equation and net ionic equation for the following reactions. If no precipitate forms, write “No reaction.”
a. BaCl2(aq) + Na2SO4(aq) Ba2+ + SO42- → BaSO4(s)
b. Pb(NO3)2(aq) + KCl(aq) Pb2+ + 2Cl- → PbCl2 (s)
c. AgNO3(aq) + Na3PO4(aq) Ag+ + PO43- → Ag3PO4(s)
d. NaOH(aq) + Fe(NO3)3(aq) Fe3+ + 3OH- → Fe(OH)3(s)
4.8. Write the balanced molecular equation, complete ionic equation and net ionic equation for the following reactions. If no precipitate forms, write “No reaction.”
a. FeSO4(aq) + KCl(aq) no reaction
b. Al(NO3)3(aq) + Ba(OH)2(aq) Al3+ + 3OH- → Al(OH)3(s)
c. CaCl2(aq) + Na2SO4(aq) Ca2+ + SO42- → CaSO4(s)
d. K2S(aq ) + Ni(NO3)2(aq) Ni2+ + S2- → NiS(s)
4.9. Give an example how each of the following insoluble ionic compounds could be produced using a precipitation reaction. Write the balanced molecular equation for each reaction.
a. Fe(OH)3(s) Fe(NO3)3 + NaOH
b. Hg2Cl2(s) Hg2(NO3)2 + NaCl
c. PbSO4(s) Pb(NO3)2 + Na2SO4
d. BaCrO4(s) Ba(NO3)2 + Na2CrO4
4.10. Write net ionic equations for the reaction, if any, that occurs when aqueous solutions of the following are mixed.
a. chromium(III) chloride and sodium hydroxide Cr3+ + 3OH- → Cr(OH)3(s)
b. silver nitrate and ammonium carbonate 2Ag+ + CO32- → Ag2CO3(s)
c. copper(II) sulfate and mercury(I) nitrate Hg22+ + SO42- → Hg2SO4(s)
d. strontium nitrate and potassium iodide no reaction
4.11. What volume of Na2CrO4 is required to precipitate all of the silver ions from 75.0 mL of a 0.100M solution of AgNO3? 250 mL
4.12. What mass of solid aluminum hydroxide can be produced when 50.0 mL of 0.200 M Al(NO)3 is added to 200.0 mL of 0.100 M KOH? 0.520 g
4.13. How many grams of silver chloride can be prepared by the reaction of 100 mL of 0.20 M silver nitrate with 100.0 mL of 0.15 M calcium chloride? Calculate the concentrations of each ion remaining in solution after precipitation is complete. 2.9g AgCl; 0.05 M Cl-; 0.10M NO3-1;
0.075M Ca2+
Acid-Base Reactions
4.14. Write the balanced molecular, complete ionic, and net ionic equations for each of the following acid-base reactions.
a. HClO4(aq) + Mg(OH)2(s) → H2O + Mg(ClO4)2
b. HCN(aq) + NaOH(aq) → H2O + NaCN
c. HCl(aq) + NaOH(aq) → H2O + NaCl
4.15. Write the balanced molecular, complete ionic, and net ionic equations for the reactions that occur when the following are mixed.
a. Solid silver hydroxide and hydrobromic acid → AgBr + H2O
b. Aqueous strontium hydroxide and hydroiodic acid → SrI2 + 2H2O
c. Solid chromium(III) hydroxide and nitric acid → 2Cr(NO3)3 + 6H2O
4.16. What volume of each of the following acids will react completely with 50.00 mL of 0.200 M NaOH?
a. 0.100 M HCl 0.100L
b. 0.150 M HNO3 66.7 mL
c. 0.200 M HC2H3O2 (1 acidic hydrogen) 50.0 mL
4.17. What volume of each of the following bases will react completely with 25.00 mL of 0.200 M HCl?
a. 0.100 M HCl 50.0 mL
b. 0.0500 M Ba(OH)2 50.0 mL
c. 0.250 M KOH 20 mL
4.18. A student titrates an unknown amount of potassium hydrogen phthalate (KHC8H4O4, often abbreviated KHP) with 20.46 mL of 0.1000 M NaOH solution. KHP (molar mass = 204.22 g/mol) has one acidic hydrogen. How many grams of KHP were titrated (reacted completely) by the sodium hydroxide solution? 0.4178 g
4.19. The concentration of a certain sodium hydroxide solution was determined by using the solution to titrate a sample of potassium hydrogen phthalate (abbreviated as KHP). KHP is an acid with one acidic hydrogen and a molar mass of 204.22 g/mol. In the titration, 34.67 mL of the sodium hydroxide solution was required to react with 0.1082 g KHP. Calculate the molarity of the sodium hydroxide. 1.528x10-2M
Oxidation-Reduction Reactions
4.20. Assign oxidation states for all atoms in each of the following compounds.
AP Chemistry Name:
Chapter 4 Review Questions Period:
a. KMnO4 1+; 7+; 2-
b. NiO2 4+; 2-
c. K4Fe(CN)6 (Fe only) 2+
d. (NH4)2HPO4 3-; 1+; 5+; 2-
e. P4O6 3+;2-
f. Fe3O4 8/3+; 2-
g. XeOF4 6+; 2-, 1-
h. SF4 4+; 1-
i. CO 2+, 2-
j. Na2C2O4
1+, 3+, 2-
AP Chemistry Name:
Chapter 4 Review Questions Period:
4.21. Assign the oxidation state for bromine in each of the following compounds.
a. HBr 1-
b. HOBr 1+
c. Br2 0
d. HBrO4 7+
e. BrF3 3+
4.22. Assign the oxidation state for nitrogen in each of the following
AP Chemistry Name:
Chapter 4 Review Questions Period:
a. Li3N 3-
b. NH3 3-
c. N2H4 2-
d. NO 2+
e. N2O 1+
f. NO2 4+
g. NO21- 3+
h. NO31- 5+
i. N2 0
AP Chemistry Name:
Chapter 4 Review Questions Period:
4.23. Specify which of the following are oxidation-reduction reactions and identify the oxidizing agent, the reducing agent, the substance being oxidized, and the substance being reduced.
a. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) (Y)
b. Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) (Y)
c. Cr2O72-(aq) + 2OH1-(aq) → 2CrO42-(aq) + 2H2O(l) (No)
d. O3(g) + NO(g) → O2(g) + NO2(g) (Y)
e. 2H2O2(l) → 2H2O(l) + O2(g) (Y)
f. 2CuCl(aq) → CuCl2(aq) + Cu(s) (Y)
4.24. Specify which of the following are oxidation-reduction reactions and identify the oxidizing agent, the reducing agent, the substance being oxidized, and the substance being reduced.
a. Cu(s) + 2Ag1+(aq) → 2Ag(s) + Cu2+(aq) (Y)
b. HCl(g) + NH3(g) → NH4Cl(s) (N)
c. SiCl4(l) + 2H2O(l) → 4HCl(aq) + SiO2(s) (N)
d. SiCl4(l) + 2Mg(s) → 2MgCl2(s) + Si(s) (Y)
e. Al(OH)41-(aq) → AlO21-(aq) + 2H2O(l) (N)
4.25. Balance the following oxidation-reduction reactions that occur in acidic solutions.
a. Zn(s) + 2HCl(aq) → Zn2+(aq) + H2(g) + 2Cl1-(aq)
b. 3I1-(aq) + 2ClO1-(aq) → I31-(aq) + Cl1-(aq) +H2O
c. 3H2O + 4H3O+ + 3As2O3(s) + 4NO31-(aq) → 6H3AsO4(aq) + 4NO(g)
d. 16H3O+ + 10Br1-(aq) + 2MnO41-(aq) → 5Br2(l) + 8Mn2+(aq) + 24H2O
e. 3CH3OH(aq) + Cr2O72-(aq) → 2CH2O(aq) + 7Cr3+(aq)
4.26. Balance the following oxidation-reduction reactions that occur in acidic solution using the half-reaction method.
a. 3Cu(s) + 3NO31-(aq) → 3Cu2+(aq) + 3NO(g)
b. Cr2O72-(aq) + 6Cl1-(aq) → 2Cr3+ + 3Cl2(g)
c. Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s)
d. 2Mn2+(aq) + 5NaBiO3(s) → 5Bi3+(aq) + 2MnO41-(aq)
e. H3AsO4(aq) + 4Zn(s) → AsH3(g) + 4Zn2+(aq)
4.27. Balance the following oxidation-reduction reactions that occur in basic solutions.
a. Al(s) + MnO41-(aq) → MnO2(s) + Al(OH)41-(aq)
b. Cl2(g) → Cl1-(aq) + OCl1-(aq)
c. NO21-(aq) + 2Al(s) → NH3(g) + 2AlO21-(aq)
4.28. Balance the following oxidation-reduction reactions that occur in basic solution.
a. Cr(s) + CrO42-(aq) → 2Cr(OH)3(s)
b. 2MnO41-(aq) + 7S2-(aq) → 2MnS(s) + 5S(s)
c. 3CN1-(aq) + 2MnO41-(aq) → 3CNO1-(aq) + 2MnNO2(s)
4.29. Gold metal will not dissolve in either concentrated nitric acid or concentrated hydrochloric acid. It will dissolve, however, in aqua regia, a mixture of the two concentrated acids. The products of the reaction are the AuCl41- ion and gaseous NO. Write a balanced equation for the dissolution of gold in aqua regia. Au 4Cl- + 4H+ + NO3- → AuCl4 + NO + 2H2O
Additional Problems
4.30. A 230.-mL sample of a 0.275 M CaCl2 solution is left on a hot plate overnight; the following morning, the solution is 1.10 M. What volume of water evaporated from the 0.275 M CaCl2 solution? 173 mL
4.31. Using the general solubility rules given in Table 4.1, name three reagents that would form precipitates with each of the following ions in aqueous solution. Write the net ionic equation for each of your suggestions.
AP Chemistry Name:
Chapter 4 Review Questions Period:
a. chloride ion
b. calcium ion
c. iron(III) ion
d. sulfate ion
e. mercury(I) ion, Hg22+
f. silver ion
AP Chemistry Name:
Chapter 4 Review Questions Period:
4.32. During the developing process of black-and-white film, silver bromide is removed from photographic film by the fixer. The major component of the fixer is sodium thiosulfate. The net ionic equation for this reaction is:
AgBr(s) + 2S2O32-(aq) → Ag(S2O3)23-(aq) + Br1-(aq)
What mass of AgBr can be dissolved by 1.00 L of 0.200 M Na2S2O3? 18.8 g
4.33. A mixture contains only NaCl and Fe(NO3)3. A 0.456-g sample of the mixture is dissolved in water, and an excess of NaOH is added, producing a precipitate of Fe(OH)3. The precipitate is filtered, dried, and weighed. Its mass is 0.107 g. Calculate the following.
a. The mass of iron in the sample 0.0559 g
b. The mass of Fe(NO3)3 in the sample 0.242 g
c. The mass percent of Fe(NO3)3 in the sample 53.1%
4.34. A 10.00-mL sample of vinegar, an aqueous solution of acetic acid (HC2H3O2), is titrated with 0.5062 M NaOH, and 16.58 mL is required to reach the equivalence point.
a. What is the molarity of the acetic acid? 0.8393 M
b. If the density of the vinegar is 1.006 g/cm3, what is the mass percent of acetic acid in the vinegar? 5.010%
4.35. A 2.20-g sample of an unknown acid (empirical formula = C3H4O3) is dissolved in 1.0 L of water. A titration required 25.0 mL of 0.500 M NaOH to react completely with all the acid present. Assuming the unknown acid has one acidic proton per molecule, what is the molecular formula of the unknown acid? C6H8O6
Challenge Problems
4.36. Complete and balance each acid-base reaction.
a. H3PO4(aq) + NaOH(aq) → Na3PO4 + 3H2O
b. H2SO4(aq) + Al(OH)3(aq) → Al2(SO4)3 + 6H2O
c. H2Se(aq) + Ba(OH)2(aq) → BaSe + 2H2O
d. H2C2O4(aq) + NaOH(aq) → NaC2O4 + 2H2O
4.37. What volume of 0.0521 M Ba(OH)2 is required to neutralize exactly 14.20 mL of 0.141 M H3PO4? Phosphoric acid contains three acidic hydrogens. 57.6 mL
Marathon Problem
4.38. Three students were asked to find the identity of the metal in a particular sulfate salt. They dissolved a 0.1472-g sample of the salt in water and treated it with excess barium chloride, resulting in the precipitation of barium sulfate. After the precipitate had been filtered and dried, it weighed 0.2327 g.
Each student analyzed the data independently and came to different conclusions. Pat decided that the metal was titanium. Chris thought it was sodium. Randy reported that it was gallium. What formula did each student assign to the sulfate salt?
Look for information on the sulfates of gallium, sodium and titanium in this text and reference books such as the CRC Handbook of Chemistry and Physics. What further tests would you suggest to determine which student is most likely correct?