1. Chemical Reactions *5 General Types Combination Decomposition
Single-Replacement
Double-Replacement
Combustion

2. Some exceptions
Some reactions may appear to fit into more than one category

3. Combination Reactions
AKA – Synthesis
Occurs when 2 or more substances combine to form a single substance
Reactants are typically 2 elements or 2 compounds
Product is always a compound

4. Group A metals react with a nonmetal – get metal cation and nonmetal anion
2Na(s) + Cl2(g) NaCl(s)

5. Two nonmetals react to form more than one compound
C(s) O2(g) CO2(g)
2C(s) O2(g) CO(g)

6. Transition metals reacting with nonmetals may give more than one product
4Cu(s) O2(g) Cu2O
copper (I) oxide
2Cu(s) O2(g) CuO
copper (II) oxide

7. Some nonmetal oxides react with water to form an acid
CO2(g) H2O H2CO3(aq)
Carbonic acid

8. Some metal oxides react with water to give a base (contains hydroxide ions)
CaO(s) + H2O(l) Ca(OH)2(aq)
Calcium hydroxide

10. Practice Mg + O Ca + S N2O5 + H2O 2Mg + O2 2MgO Ca + S CaS
N2O H2O HNO3

11. Decomposition Reactions
Single compound breaks down into 2 or more products
Products can be any combination of elements and compounds
CaCO3(s) heat CaO(s) + CO2(g)

12. Hard to predict products of decomposition reaction, unless it’s a binary compound
Breaks down into constituent elements
Often requires energy in form of heat, light or electricity

13. Extremely rapid decomposition reactions produce gases and heat
Often cause explosions
Example: dynamite

15. Practice Ag2O(s) Nickel(II) Carbonate Nickel(II) oxide + ?
2AgO(s) 4Ag(s) +O2(g) NiCO3 NiO + CO2 (g)

16. Single-Replacement Reactions
Add Na to water = violent reaction
Produces H can ignite
This is a single-replacement reaction:
One element replaces a second element in a compound
AKA: single-displacement reaction

17. 2Na(s) + 2H2O(l) H2(g) + 2NaOH(aq)

18. Whether a metal replaces another metal in a reaction is determined by relative reactivities.
The activity series of metals lists metals in order of decreasing activity.
A reactive metal will replace any metal listed below it on the chart.

20. K replaces Na, Al, or Zn
Fe will not replace Mg, Ca, or Li
K(s) + NaNO3(aq) KNO3(aq) + Na(s)
Fe(s) + Ca(NO3)2(aq) no reaction

21. Nonmetals can also replace nonmetals
Limited to halogens
Activity decreases as you go down the family

23. Practice Ag(s) + KNO3(aq) Zn(s) + AgNO3(aq) No reaction
Zn(NO3)2(aq) + 2Ag(s)

24. Double-Replacement Reaction
When ionic solids dissolve in water- form homogeneous mixtures.
If 2 or more ionic solutions are mixed:
A) get aqueous homogeneous mixtures
B) chemical reaction will occur

25. K2CO3(aq) + BaCl2(aq) 2KCl(aq) + BaCO3(s) A reaction occurred- white precipitate formed

26. Double-replacement reactions involve exchange of positive ions between reacting compounds
One product precipitates from solution
One product is a gas that bubbles out
One product is a molecular compound like water

28. Practice
HCl(aq) + Ca(OH)2(aq) 2HCl(aq) + Ca(OH)2(aq) CaCl2(aq) + 2H2O(l) Ag2SO4(aq) + AlCl3(aq) 3Ag2SO4(aq) + 2AlCl3(aq) 6AgCl(s) + Al2(SO4)3(aq)

29. Combustion Reactions Element or compound reacts with oxygen
Usually produces energy as heat & light
Usually involves hydrocarbons (hydrogen & carbon)

30. Complete combustion yields CO2 + H2O
Incomplete combustion (lack of O2) may also yield C and CO
2C2H2(g) + 5O2(g)
4CO2(g) H2O(g)

31. Reactions between some elements + O2 are also combustion reactions
2Mg(s) + O2(g) MgO(s)
This can also be classified as a combination reaction

33. Practice Complete combustion of C4H8 Butane C4H8 + 6O2 4CO2 + 4H2O
Complete combustion of C8H18 Octane
2C8H O CO H2O

34. Exceptions Some reactions don’t fit any of these five types
Example- Oxidation-reduction reaction (discussed in chapter 20)