Chemistry 1000 A
Fall 2004
Third assignment
Classes of Chemical Reactions and Stoichiometry
Responsible sections of Oxtoby, 4th edition: Chapter 2 & 4, in their entirety.
Self-Study Assignment
Review Questions
Learn the names, symbols, charges and solubility problems of the common ions listed in the Text and in the Ionic
Compounds sheet on the web page.
Learn the six classes of chemical reactions and practice classifying reactions by these categories.
Learn the locations and formulas of the element oxides of the main group of the PT.
Learn the rules for assigning oxidation number and practice applying them.
Be sure to be able to do each of the main types of Stoichiometry problems. All problems dealing with quantity of matter of
chemical reagents are essentially related, and to a certain extent, each problem is unique. Therefore a good understanding of
the concepts, along with enough practice to overcome silly mistakes, should be your goal. Attempting to solve problems by
memorizing rote methodology is bad practice!
Study Questions from the end of Chapter 2
a) From the main section of Problems, all the problems are relevant. As usual, you are strongly advised to try at least
several different-looking problems from each section. Note that the first two sections are very elementary!
b) From the Additional Problems, all are relevant but are fairly advanced (good for review!)
Study Questions from the end of Chapter 4
a) From the main section of Problems, all the problems are relevant. As usual, you are strongly advised to try at least
several different-looking problems from each section.
b) From the Additional Problems, all are relevant but are fairly advanced (good for review!)
Problem Set #3
1. Balance the following equations, and name the reaction products:
(a) UO2(s) + HF(l) → UF4(s) + H2O(l)
(b) NH3(aq) + HNO3(aq) → N2(g) + H2O(l)
(c) BF3(g) + H2O(l) → HF(aq) + H3BO3(aq)
2.
Which compound or compounds in each of the following groups is (are) expected to be soluble in water? If it is soluble,
state which ions are produced in water.
(a) PbSO4, Pb(NO3)2, and PbCO3
(b) Na2SO4, NaClO4, and NaCH3CO2
(c) AgBr, KBr, Al2Br6
3.
Phosphoric acid can supply one, two, or three H+ ions in aqueous solution. Write balanced equations to show this
successive loss of hydrogen ions.
4.
Balance each of the following equations, and then write the net ionic equation:
(a) (NH4)2CO3(aq) + Cu(NO3)2(aq) → CuCO3(s) + NH4NO3(aq)
(b) Pb(OH)2(s) + HCl(aq) → PbCl2(s) + H2O(l)
(c) BaCO3(s) + HCl(aq) → BaCl2(aq) + H2O(l) + CO2(g)
(d) HCl(aq) + MnO2(s) → MnCl2(aq) + Cl2(g) + H2O(l)
5.
Balance each of these equations and then classify each one as an acid-base reaction, a precipitation, or a gas-forming
reaction. Justify your classification:
(a) Ba(OH)2(s) + HCl(aq) → BaCl2 + H2O
(b) HNO3(aq) + CoCO3(s) → Co(NO3)2 + H2O + CO2
(c) Na3PO4(aq) + Cu(NO3)2(aq) → Cu3(PO4)2 + NaNO3
(e) Fe(OH)3(s) + HNO3(aq) → Fe(NO3)3 + H2O
(f) FeCO3(s) + HNO3(aq) → Fe(NO3)2 + CO2 + H2O
(g) FeCl2(aq) + (NH4)2S(aq) → FeS + NH4Cl
(h) Fe(NO3)2(aq) + Na2CO3(aq) → FeCO3 + NaNO3
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6.
Complete and balance the following acid-base reactions. Name the reactants and products.
(a) H3PO4(aq) + KOH(aq) →
(H2C2O4 is oxalic acid, an acid capable of donating two H+ ions.)
(b) H2C2O4(aq) + Ca(OH)2(s) →
7.
Many minerals are metal carbonates, and siderite is a mineral that consists largely of iron(II) carbonate. Write an
overall, balanced equation for the reaction of the main constituent of the mineral with sulfuric acid, and name each
reactant and product
8.
Determine the oxidation number of each element in the following ions or compounds:
(b) H2AsO4–
(c) C2H4O2
(d) N2O4
(e) C5H8O2
(f) XeO42–
(a) SF6
9.
Which of the following reactions are oxidation-reduction reactions? Explain your answer in each case. Classify the
remaining reactions.
(a) Zn(s) + 2 NO3–(aq) + 4 H+(aq) → Zn2+(aq) + 2 NO2(g) +2 H2O(l)
(b) Zn(OH)2(s) + H2SO4(aq) → ZnSO4(aq) + 2 H2O(l)
(c) Ca(s) +2 H2O(l) → Ca(OH)2(s) + H2(g)
10. In each of the following reactions, tell which reactant is oxidized and which is reduced. Designate the oxidizing agent
and reducing agent.
(a) Ca(s) + 2 HCl(aq) → CaCl2(aq) + H2(g)
(b) Cr2O72–(aq) + 3 Sn2+(aq) + 14 H+(aq) → 2 Cr3+(aq) + 3 Sn4+(aq) +7 H2O(l)
(c) FeS(s) + 3 NO3– (aq) + 4 H+(aq) → 3 NO(g)+SO42–(aq) + Fe3+(aq) +2 H2O(l)
11. Aspirin (C9H8O4) is produced by the reaction of salicylic acid (C7H6O3) and acetic anhydride (C4H6O3):
C7H6O3 (s) + C4H6O3 (l) Æ C9H8O4 (s) + CH3COOH (l)
If you mix 100. g of each of the reactants, what is the maximum mass of aspirin that can be obtained?
12. An unknown metal reacts with oxygen to give the metal oxide, MO2. Identify the metal based on the following information:
Mass of metal = 0.356 g
Mass of sample after converting metal completely to oxide = 0.452 g
13. To analyze an iron-containing compound, you convert all the iron to Fe2+ in aqueous solution and then titrate the
solution with aqueous KMnO4 according to the following balanced, net ionic equation:
MnO4– (aq) + 5 Fe2+ (aq) + 8 H+ (aq) Æ Mn2+ (aq) + 5 Fe3+ (aq) + 4 H2O(l)
If a 0.598-g sample of the iron-containing compound re-quires 22.25 mL of 0.0123 M KMnO4 for titration to the
equivalence point, what is the weight percent of iron in the compound?
14. Aluminum bromide, a valuable laboratory chemical, is made by the direct reaction of the elements:
2 Al (s) + 3 Br2 (l) Æ Al2Br6 (s)
What is the theoretical yield in grams of Al2Br6 if 25.00 mL of liquid bromine (density = 3.100 g mL–1) and 12.5 g
aluminum metal are used? Is any aluminum or bromine left over when the reaction has gone to completion? If so,
what mass of which reactant remains?
15. Boron forms an extensive series of compounds with hydrogen, all with the general formula BxHy.
+ n O2 (g) Æ B2O3 (s) + H2O (g)
BxHy (s)
If 0.1615 g of BxHy gives 0.4217 g of B2O3 when burned in excess O2 , what is the empirical formula of BxHy? In a
separate experiment, the approximate molar mass of the same boron hydride was determined by osmometry to be 52.9
g mol–1. What is the molecular formula of BxHy?
16. A mixture of sodium carbonate and sodium hydrogen carbonate is treated with aqueous hydrochloric acid. The
unbalanced equations for the resulting reactions are:
Na2CO3 (s) + HCl (aq) Æ NaCl (aq) + CO2 (g) + H2O (l)
NaHCO3 (s) + HCl (aq) Æ NaCl (aq) + CO2 (g) + H2O (l)
You treat 9.450 g of a Na2CO3/ NaHCO3 mixture with an excess of aqueous HCl and isolate after evaporation 9.355 g
of NaCl. What is the weight percent of each substance in the mixture? What happens to the unreacted HCl upon
evaporation, and what does this suggest about the appropriate place to conduct this experiment?
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