1. Types of Reactions I. Synthesis reactions – have only one product.
General Form: A + X  AX
2 Na(s) + Cl2(g)  2 NaCl(s)
2 H2(g) + O2(g)  2 H2O(l)
CaO(s) + CO2(g)  CaCO3(s)
EX:

2. Synthesis Reactions Examples: N2 (g) + 3 H2 (g)  2 NH3 (g)
Two or more substances react to form one product
Also called “combination rxns”
Examples:
N2 (g) + 3 H2 (g)  2 NH3 (g)
C3H6 (g) + Br2 (l)  C3H6Br2 (l)
2 Mg (s) + O2 (g)  2 MgO (s)

3. II. Decomposition Reactions
Have only one reactant
General Form: AX  A + X
One substance breaks down into two or more substances
Examples:
CaCO3 (s)  CaO (s) + CO2 (g)
2 KClO3 (s)  2 KCl (s) + O2 (g)
2 NaN3 (s)  2 Na (s) + 3 N2 (g)

4. Electrolysis – decomposing a compound by running an electric current through it.
2 H2O  2 H2 + O2

5. III. Single Replacement Reactions
An element replaces another element in a compound.
General forms:
A + BX  B + AX (metal takes place of metal) or
Y + BX  X + BY (nonmetal takes place of nonmetal)
These rxns usually occur in solution.

6. EX: Cu(s)+ 2 AgNO3(aq)  2 Ag(s) + Cu(NO3)2(aq)
Cl2(g) + 2 NaBr2(aq)  Br2(l) + 2 NaCl(aq)

7. *** For a single replacement rxn to occur, an element must be more reactive than the element it replaces***
See the “Activity Series of Elements” on the back of your periodic table. In order for an element to replace another element in a compound, it must be higher than that element on the activity series.
Cu(s)+ 2 AgNO3(aq)  2 Ag(s) + Cu(NO3)2(aq)
Occurs - Copper is more reactive than silver
Cl2(g) + 2 NaBr2(aq)  Br2(l) + 2 NaCl(aq)
Occurs - Chlorine is more reactive than bromine

8. Aluminum is LESS reactive than sodium.
Al(s) + NaCl(aq) 
No Rxn
Aluminum is LESS reactive than sodium.
No Rxn
Br2(l) + NaCl(aq) 
Bromine is LESS reactive than chlorine
Remember that metals replace metals,
and nonmetals replace nonmetals.

9. If the following rxns occur, write the products and balance the equation; if no reaction occurs, write “No Rxn”
1. Mg(s) + ZnCl2(aq) 
2. Al(s) + Pb(NO3)2(aq) 
3. Fe(s) + AlCl3(aq) 
4. I2(s) + NaCl(aq) 
5. F2(g) + LiBr(aq) 
Zn(s) + MgCl2(aq) 2 3
Pb(s) + Al(NO3)3(aq)
No Rxn
No Rxn 2
Br2(l) + LiF(aq)

10. Special Single Replacement Reactions
Write the equation for the rxn of potassium and water.
a) Group 1 metals and Ca, Sr, and Ba will replace one of the hydrogens in water, producing hydrogen gas and the metal hydroxide.
Ex: Ca + 2 H2O  H2 + Ca(OH)2
2 K + 2 H2O  H2 + 2 KOH

11. b) Metals can replace the hydrogen in acids.
Ex: 2 Al(s) + 6 HCl(aq)  3 H2(g) + 2 AlCl3(aq)
*note that hydrogen is listed with the metals on the Activity Series
Write the equation for the rxn between nitric acid and magnesium metal.
Mg HNO3  H2 + Mg(NO3)2

12. IV. Double-Replacement Rxns
- the ions of two aqueous compounds “switch places” to form two new compounds.
General Form: AX + BY  AY + BX
EX: AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)

13. In order for a double replacement rxn to occur, one of the products must remove its ions from aqueous solution. This can occur when:
1) One of the products is insoluble (or only slightly soluble) in water. A precipitate forms. See the solubility chart on back of periodic table.
Pb(NO3)2(aq) + Na2CrO4(aq)  PbCrO4(s) + 2NaNO3(aq)
If there is anything other than “s” on the solubility table, that substance is the precipitate and the rxn occurs. If both products are soluble, no rxn occurs.

14. Predict the products and balance the equations for the following rxns; if no reaction occurs write “no rxn”
(aq)
1. AlCl3(aq) + Na3PO4(aq) 
2. KNO3(aq) + MgBr2(aq) 
AlPO NaCl
(s) 3
No Rxn
NaCl(aq) + Pb(NO3)2(aq) 
4. KNO3(aq) + CaCl2(aq) 
5. BaI2(aq) + Na2CO3(aq) 
6. CuSO4(aq) + K3PO4(aq) 
7. (NH4)2S(aq) + ZnCl2(aq)  2
PbCl2(s) + NaNO3(aq)
No Rxn
BaCO3(s) + 2 NaI(aq)

15. 2. A double replacement rxn occurs if one of the products is water (H2O).
Ex: HCl(aq) + NaOH(aq)  H2O(l) + NaCl(aq)
2 HNO3(aq) + Mg(OH)2(s)  H2O(l) + 2 Mg(NO3)2(aq)
(these rxns occur when an acid reacts with a base – they’re called neutralization rxns)
Predict the products and balance the following rxn:
H2SO4(aq) + KOH(aq) 

16. *metal carbonates react with acids to produce H2O, CO2, and a salt.
3. A double replacement rxn occurs if one of the products is a gas.
Ex: 2 HCl(aq) + Na2CO3(aq)  H2CO3(aq) + 2NaCl(aq)
2 HCl(aq) + Na2CO3(aq)  H2O(l) +CO2(g) + 2NaCl(aq)
*metal carbonates react with acids to produce H2O, CO2, and a salt.
Predict the products and balance the following rxn:
H2SO4(aq) + CaCO3(aq) 