The Foundations of Chemistry

4-10 Summary of Reaction Types 161

TABLE 4-14 Summary and Examples of Reaction Types

Section Reaction Type, Examples Characteristics

4-5 Oxidation-Reduction (Redox) Oxidation numbers (Sec. 4-4) of some elements change;

at least one element must increase and at least one

must decrease in oxidation number.

4-6 Combination More than one reactant, single product

1. Element
   element ncompound
   2Al(s)
   3Cl 2 (g) n2AlCl 3 (s)
   P 4 (s)
   10Cl 2 (g) n4PCl 5 (s)


2. Compound
   element ncompound
   SF 4 (g)
   F 2 (g) nSF 6 (g)
   2SO 2 (g)
   O 2 (g) n2SO 3 (
   )


3. Compound
   compound ncompound
   CaO(s)
   CO 2 (g) nCaCO 3 (s)
   Na 2 O(s)
   H 2 O(
   ) n2NaOH(aq)

4-7 Decomposition Single reactant, more than one product

1. Compound nelement
   element
   2HgO(s) n2Hg(g)
   O 2 (g)
   2H 2 O(
   ) n2H 2 (g)
   O 2 (g)


2. Compound ncompound
   element
   2NaNO 3 (s) n2NaNO 2 (s)
   O 2 (g)
   2H 2 O 2 (
   ) n2H 2 O(
   )
   O 2 (g)


3. Compound ncompound
   compound
   CaCO 3 (s) nCaO(s)
   CO 2 (g)
   Mg(OH) 2 (s) nMgO(s)
   H 2 O(
   )

4-8 Displacement One element displaces another from a compound:

Zn(s)
CuSO 4 (aq) nCu(s)
ZnSO 4 (aq)* Element
compound nelement
compound

Zn(s)
H 2 SO 4 (aq) nH 2 (g)
ZnSO 4 (aq)* Activity series (Table 4-12) summarizes metals and

Cl 2 (g)
2NaI(aq) nI 2 (s)
2NaCl(aq)* hydrogen; halogen activities (Group VIIA) decrease

going down the group

4-9 Metathesis Positive and negative ions in two compounds appear to

“change partners” to form two new compounds; no

change in oxidation numbers

1. Acid-base neutralization Product is a salt; water is often formed
   HCl(aq)
   NaOH(aq) nNaCl(aq)
   H 2 O(
   )
   CH 3 COOH(aq)
   KOH(aq) nKCH 3 COO(aq)
   H 2 O(
   )
   HCl(aq)
   NH 3 (aq) nNH 4 Cl(aq)
   2H 3 PO 4 (aq)
   3Ca(OH) 2 (aq) nCa 3 (PO 4 ) 2 (s)
   6H 2 O(
   )†


2. Precipitation Products include an insoluble substance, which
   CaCl 2 (aq)
   Na 2 CO 3 (aq) nCaCO 3 (s)
   2NaCl(aq) precipitates from solution as a solid; solubility
   Pb(NO 3 ) 2 (aq)
   K 2 CrO 4 (aq) nPbCrO 4 (s)
   2KNO 3 (aq) guidelines assist in predicting, recognizing
   2H 3 PO 4 (aq)
   3Ca(OH) 2 (aq) nCa 3 (PO 4 ) 2 (s)
   6H 2 O(
   )†


3. Gas-formation Products include an insoluble or slightly soluble gas,
   2HCl(aq)
   CaCO 3 (s) nCO 2 (g)
   H 2 O(
   )
   CaCl 2 (aq) which escapes from solution
   MnS(s)
   2HCl(aq) nMnCl 2 (aq)
   H 2 S(g)

*These examples are also oxidation-reduction (redox) reactions.
†This reaction is both an acid-base neutralization reaction and a precipitation reaction.