170 CHAPTER 4: Some Types of Chemical Reactions
38.Assign oxidation numbers to the element specified in each
group of compounds.
(a) P in PCl 3 , P 4 O 6 , P 4 O 10 , HPO 3 , H 3 PO 3 , POCl 3 ,
H 4 P 2 O 7 , Mg 3 (PO 4 ) 2
(b) Cl in Cl 2 , HCl, HClO, HClO 2 , KClO 3 , Cl 2 O 7 ,
Ca(ClO 4 ) 2
(c) Mn in MnO, MnO 2 , Mn(OH) 2 , K 2 MnO 4 , KMnO 4 ,
Mn 2 O 7
(d) O in OF 2 , Na 2 O, Na 2 O 2 , KO 2
39.Assign oxidation numbers to the element specified in each
group of ions.
(a) S in S^2 , SO 32 , SO 42 , S 2 O 32 , S 4 O 62 , HS
(b) Cr in CrO 2 , Cr(OH) 4 , CrO 42 , Cr 2 O 72
(c) B in BO 2 , BO 33 , B 4 O 72
40.Assign oxidation numbers to the element specified in each
group of ions.
(a) N in N^3 , NO 2 , NO 3 , N 3 , NH 4
(b) Br in Br, BrO, BrO 2 , BrO 3 , BrO 4 Oxidation – Reduction Reactions
41.Define and illustrate the following terms: (a) oxidation,
(b) reduction, (c) oxidizing agent, (d) reducing agent.
42.Why must oxidation and reduction always occur simulta-
neously in chemical reactions?
43.Determine which of the following are oxidation–reduction
reactions. For those that are, identify the oxidizing and
reducing agents.
(a) 3Zn(s)2CoCl 3 (aq) n3ZnCl 2 (aq)2Co(s)
(b) ICl(s)H 2 O() nHCl(aq)HIO(aq)
(c) 3HCl(aq)HNO 3 (aq) n
Cl 2 (g)NOCl(g)2H 2 O()
heat
(d) Fe 2 O 3 (s)3CO(g) 888n2Fe(s)3CO 2 (g)
44.Determine which of the following are oxidation–reduction
reactions. For those that are, identify the oxidizing and
reducing agents.
(a) HgCl 2 (aq)2KI(aq) nHgI 2 (s)2KCl(aq)
(b) 4NH 3 (g)3O 2 (g) n2N 2 (g)6H 2 O(g)
(c) CaCO 3 (s)2HNO 3 (aq) n
Ca(NO 3 ) 2 (aq)CO 2 (g)H 2 O()
(d) PCl 3 ()3H 2 O() n3HCl(aq)H 3 PO 3 (aq)
45.Write balanced formula unit equations for the following
redox reactions:
(a) aluminum reacts with sulfuric acid, H 2 SO 4 , to pro-
duce aluminum sulfate, Al 2 (SO 4 ) 3 , and hydrogen
(b) nitrogen, N 2 , reacts with hydrogen, H 2 , to form
ammonia, NH 3
(c) zinc sulfide, ZnS, reacts with oxygen, O 2 , to form zinc
oxide, ZnO, and sulfur dioxide, SO 2
(d) carbon reacts with nitric acid, HNO 3 , to produce
nitrogen dioxide, NO 2 , carbon dioxide, CO 2 , and
water
(e) sulfuric acid reacts with hydrogen iodide, HI, to pro-
duce sulfur dioxide, SO 2 , iodine, I 2 , and water46.Identify the oxidizing agents and reducing agents in the
oxidation–reduction reactions given in Exercise 45.
47.Write total ionic and net ionic equations for the follow-
ing redox reactions occurring in aqueous solution or in
contact with water:
(a) Fe2HCl88nFeCl 2 H 2
(b) 2KMnO 4 16HCl88n
2MnCl 2 2KCl5Cl 2 8H 2 O
(Note: MnCl 2 is water-soluble.)
(c) 4Zn10HNO 3 88n
4Zn(NO 3 ) 2 NH 4 NO 3 3H 2 O.
48.The air we inhale contains O 2. We exhale CO 2 and H 2 O.
Does this suggest that our bodily processes involve oxida-
tion? Why?Combination Reactions
49.Write balanced equations that show the combination reac-
tions of the following Group IA metals combining with
the Group VIIA nonmetals. (a) Li and Cl 2 , (b) K and F 2 ,
(c) Na and I 2
50.Write balanced equations that show the combination reac-
tions of the following Group IIA metals and Group VIIA
nonmetals. (a) Be and F 2 , (b) Ca and Br 2 , (c) Ba and Cl 2
51.Phosphorus and fluorine can react to form two com-
pounds. Write balanced equations for these reactions.
Which reaction requires excess phosphorus and which
requires excess fluorine?
52.Two binary compounds contain arsenic and chlorine.
What are their formulas? Under what conditions could
each be formed?
In Exercises 53 and 54, some combination reactions are de-
scribed by words. Write the balanced chemical equation for each,
and assign oxidation numbers to elements other than H and O.
53.(a) Antimony reacts with a limited amount of chlorine to
form antimony(III) chloride.
(b) Antimony(III) chloride reacts with excess chlorine to
form antimony(V) chloride.
(c) Carbon burns in a limited amount of oxygen to form
carbon monoxide.
54.(a) Sulfur trioxide reacts with aluminum oxide to form
aluminum sulfate.
(b) Dichlorine heptoxide reacts with water to form per-
chloric acid.
(c) When cement “sets,” the main reaction is the combi-
nation of calcium oxide with silicon dioxide to form
calcium silicate, CaSiO 3.Decomposition Reactions
In Exercises 55 and 56, write balanced formula unit equations
for the reactions described by words. Assign oxidation numbers
to all elements.
55.(a) Hydrogen peroxide, H 2 O 2 , is used as an antiseptic.
Blood causes it to decompose into water and oxygen.