1. Types of Reactions

2. 5 Types of Chemical Reactions
Synthesis (Combination) reaction
A B  AB
Decomposition reaction
AB  A + B
Combustion reaction (of a hydrocarbon)
CxHy O2  CO2 + H2O + energy
ASingle-replacement reaction
A BC  AC + B
Objective:
To classify a chemical reaction as one of the following types: combination (synthesis), decomposition, single replacement, double replacement, or neutralization.
BDouble-replacement reaction
AB CD  AD + CB
Ause activity series to predict
B use solubility chart to predict

3. Synthesis Reactions General Formula: A + B  AB A is an element
(identifying characteristic: only ONE product!)
A is an element
B is an element
AB is a compound
Hints!! Don’t forget the formulas for diatomic elements, aka the “7-ups”
Always write the correct formula for the compound based on the charges of the ions BEFORE balancing!

4. Synthesis Reaction Na(s) + Cl2(g)  NaCl Na(s) + Cl2(g)  NaCl (s)
Example: Sodium + chlorine
1. Write the formulas for the reactant elements, including states of matter
2. Write the correct formula for the product compound based on the charge of the ions (remember that ionic compounds are solid at room temperature unless they are dissolved in water).
Na1+
Cl1-
3. Balance the equation
Na(s) Cl2(g) 
NaCl 2
Na(s) Cl2(g)  NaCl (s) 2

5. Synthesis Reaction Direct combination reaction (Synthesis)
2 Na Cl  NaCl Na Cl
Na+
Cl - Cl
Cl -
Na+ Na
General form: A B  AB
element element compound

6. Try this one!
Potassium + oxygen

7. The answer is….. 4 K(s) + O2 (g) 2 K2O (s) Write the ions K1+ O2- K O
CrissCross the charges
K2O
Reduce if needed, ignore “1”

8. Decomposition Reactions
General formula: AB  A + B
Identifying characteristic: only ONE reactant!
AB is a compound A is an element
B is an element

9. Decomposition Reaction
Ex: decomposition of water
Write the formula of the reactant compound
2. Write the formulas of the element products
3. Balance the equation 2
H2O(l) 2
H2(g) +
O2(g)

10. Decomposition Reaction
2 H2O(l)
2 H2 (g) +
O2 (g) H O H H O H + O H O H H H
General form: AB A + B
compound
two or more elements
or compounds

11. Try this one! The decomposition of iron(III) oxide
(HINT: the roman numeral tells you the charge of the iron!)
2 Fe2O3(s) Fe(s) O2(g)

12. Combustion Reactions CxHy + O2  CO2 + H2O + energy
A hydrocarbon*
Identifying characteristic: hydrocarbon and oxygen
A hydrocarbon is a molecule that consists of carbon and hydrogen

13. Tips on Balancing Combustion Reactions
Do an Atom Inventory
1st, balance the carbons
2nd, balance the hydrogens
3rd, balance the oxygens
If the oxygens don’t balance with a whole number, balance with a ½ number, THEN multiply all coefficients by 2.

14. Combustion of a Hydrocarbon
Many homes get heat from propane (C3H8) heaters.
Write a balanced chemical equation for the complete
combustion of propane gas.

15. C3H8(g) + O2(g)  CO2(g) + H2O(g) + energy 5 3 41 / 3 / 8 H 2 8 10 2 / O / 10 / 3 7
Do an Atom Inventory
1st Balance Carbons
2nd Balance hydrogens
3rd Balance oxygens

16. Combustion of Methane Gas+
One methane
molecule
Two oxygen
molecules
One carbon
dioxide molecule
Two water
molecules
Heat and flame
CH4 +
2 O2
CO2 +
2H2O
+ energy
1 carbon +
4 hydrogen
1 carbon +
2 oxygen
2 oxygen +
4 hydrogen
4 oxygen
Davis, Metcalfe, Williams, Castka, Modern Chemistry, 1999, page 245

17. Try this one!
Write the complete combustion equation for butane gas (formula for butane is C4H10). Butane is the gas found in lighters.

18. The answer is……. 2 C4H10 + 13 O2 8 CO2 + 10 H2O + energy 4 5 6.5 2 13
1. Balance C: C4H O CO H2O + energy
2. Balance H: C4H O CO H2O + energy 5
3. Balance O: C4H O CO H2O + energy
6.5
(hint: need to use a ½)
4. Double all coefficients: 2 13
C4H O CO H2O + energy 8 10

19. Single Replacement Reactions
General Formula: A + BC  B + AC
Identifying characteristic: reactants
are an ELEMENT and a COMPOUND
A is an element
BC is a compound
A and B switch places to form:
B (an element) and AC (a compound)
Need to use an Activity Series to
determine if a reaction will occur

20. Single Replacement Reactions
Mg CuSO4  MgSO Cu
General form:
A BC  AC B
How do you know if Mg switches places with
the Cu or the SO4?
If the element A forms a cation, it replaces the cation in the compound BC
If the element A forms an anion, it replaces the anion in the compound BC

21. Help, I need a review!! Ionic Compounds are ALWAYS
What is a cation and an anion?
An anion is a “-” charged ion
A cation is a “+” charged ion
Ionic Compounds are ALWAYS
written cation then anion!!
Ex: MgCl Mg Cl1-

22. Activity Series: Will a reaction occur ?
The cation list
Al(s) CuSO4 (aq)
Element Reactivity
The anion list Li Rb K Ba Ca Na Mg Al Mn Zn Cr Fe Ni Sn Pb H2 Cu Hg Ag Pt Au
Al (the element) is higher on the chart than Cu (in the compound)
Halogen Reactivity F2
Cl2
Br2 I2 Al
Al is STRONGER so overtakes/ replaces Cu in the compound and
Kicks Cu out by itself! Al
Foiled again!
Aluminum beats Copper! Cu Cu

23. Aluminum vs copper II sulfate2
Al (s) CuSO4 (aq) 3 Cu 3
+ Al2(SO4)3(aq)
(s)
Al is higher on the chart than Cu, so it kicks Cu out of the compound.
Al then makes a compound with SO4
Al SO42- 3 2
Al (SO4)
Now, balance the equation.

24. Your turn! Will a reaction occur? Yes or No
Element Reactivity
Will a reaction occur? Yes or No
If “Yes”, write a complete balanced equation Li Rb K Ba Ca Na Mg Al Mn Zn Cr Fe Ni Sn Pb H2 Cu Hg Ag Pt Au
Halogens F2
Cl2
Br2 I2
NaNO3(aq) + Ag(s) ?? F2(g) NaI(aq) ??

25. The Answers… NaNO3(aq) + Ag(s) NR (abbrev for no reaction)
Why? Because Ag (the element) is NOT higher on the chart than Na
F2(g) NaI(aq) NaF(aq) I2(g)
Why? Because F2 IS higher on the chart than I2
Since F2 becomes the F- anion, it replaces the anion in NaI

26. Potassium reacts with Water
P O W ! *
2 HOH
* Often times it helps to think of water as HOH

27. Double Replacement Reactions
AB + CD  CB + AD
Identifying characteristic:
Both reactants are ionic compounds
Watch how the cations switch places!
A reaction ONLY occurs if at least ONE of the products is
a solid (or H2O).
A solubility chart is needed to determine if the products are
solids or remain dissolved (aqueous).

28. Will Al(NO3)3 dissolve in water
Will barium phosphate dissolve in water?
Will PbI2 dissolve in water?
Yes No

29. Double Replacement Reactions Will a reaction occur?
K2CO3(aq) BaCl2(aq)
BaCO KCl 2
(s)
(aq)
1. Determine the two products based on the charge of the ions
Using the solubility chart, determine if each product is a. Aqueous (which means it is soluble in water) b. Solid (which means it is insoluble in water)
If one of the products is a solid, the reaction occurs, so BALANCE it
If BOTH products are aqueous, then NO REACTION occurs. Cross out products and write “NR”

30. Double Replacement Reaction

31. Double Replacement PracticeNR
NaCl (aq) + KNO 3(aq)
NaNO3(aq) KCl (aq)
(NH4)2CO3(aq) HOH(l)
H2CO3(aq) NH4(OH)(aq)
AgNO3(aq) KCl(aq)

32. Formation of a solid AgCl
AgNO3(aq) + KCl(aq)  KNO3 (aq) + AgCl(s)