1. CHEMICAL REACTIONS & EQUATIONS

2. Chemical Reactions

3. Chemical Reactions
Process in which one or more substances are converted into new substances with different physical and chemical properties
For example, a yellow solid precipitate, lead iodide (PbI2), forms from the mixture of two clear liquids, potassium iodide (KI) and lead nitrate (Pb(NO3)2).

4. Word Equation
Hydrogen + Oxygen
Water + Energy
Reactants
Products

5. Classification of Chemical Reactions
1. Synthesis
2. Decomposition
3. Single Replacement
4. Combustion (burning)

6. A B AB Synthesis Examples: 1 2 Cu + O2 CuO 1 H2CO3 CO2 + H2O
Two reactants combine to form a single product (compound). A B AB
One Product
Examples: 1 2
Cu O2
CuO 1
H2CO3
CO H2O

7. AB A B Decomposition Examples: 2 3 KClO3 KCl + O2 1 2 H2O2 H2O + O2
One reactant breaks down to form two or more products. AB A B
One Reactant
Examples: 2 3
KClO3
KCl O2 1 2
H2O2
H2O O2

8. A BC AC B Single Replacement Examples: 2 1 Mg + HCl MgCl2 + H2 2 1
One element replaces another from a compound A BC AC B
Examples: 2 1
Mg + HCl
MgCl H2 2 1
Cl KI
KCl I2

9. Combustion (burning) CxHy+ O2 CO2 + H2O C3H8 + O2 CO2 + H2O C2H2+ O2
Produces light and heat
CxHy+ O2
CO2 + H2O
Balance C 1st, then H, then O (because it splits up) 4 1
C3H O2 5
CO H2O 3 1 2
2.5 5 2 4 2 1
C2H2+ O2
CO H2O

10. Classification of Equations
SYNTHESIS AB A B Ca S
CaS
DECOMPOSITION AB A B
2HgO
2Hg O2

11. Classification of Equations
SINGLE
REPLACEMENT BC AB C A
2KCl
Br2
Cl2
2KBr

12. Rules for Balancing Equations
1. Obey the LAW OF CONSERVATION OF MASS.
Same number of each kind of atom on both sides of the equation.
25g +
25g +
50 g
50 g +
150 g ?g

13. How to Balance an Equation
2. To balance atoms of reactants and products, change ONLY the coefficients.
3. Do NOT change the chemical formula to balance numbers of atoms.
Numbers IN FRONT of the formulas
NOTE: Subscripts are lower numbers in formula
4 Al2O3
Coefficient
Subscripts

14. How to Balance an Equation cont.
4. Check your work by counting atoms of each element.
6. Check to see that the coefficients are in the lowest whole number ratio.
2H2O (l)
2H2 (g) + 1O2 (g)
4 Hydrogen
4 Hydrogen
2 Oxygen
2 Oxygen

15. Practice Balancing These Equations
Ca O2
CaO 2 1 2
1 Ca
1 Ca
2 O
1 O
*Hint: Start by making the uneven side even.
2 O
2 O
1 Ca
2 Ca
2 Ca
2 Ca
2 O
2 O
2 Ca, 2 O
2 Ca, 2 O

16. Practice 1 2 1 2 CH4 + O2 CO2 + H2O 2 O 3 O 4 O 4 O 1 C 1 C 4 H 4 H
*Hint: Start with the element that is split up: Oxygen.
Then, make uneven side even.
2 O
3 O
4 O
4 O
1 C
1 C
4 H
4 H
1 C, 4 H, 4 O
1 C, 4 H, 4 O

17. Practice
Fe Cl2
FeCl3 2 1 3 2
1 Fe
1 Fe
2 Cl
3 Cl
6 Cl
6 Cl
1 Fe
2 Fe
2 Fe
2 Fe
2 Fe, 6 Cl2
2 Fe, 6 Cl2

18. Practice 2 HgO Hg + O2 2 1 1 3 2 Al + MnO Al2O3 + Mn 3 2 Al, 3 Mn, 3 O
Br NaI
NaBr I2 1 2
2 Br, 2 Na, 2 I
2 Br, 2 Na, 2 I
Do these on own 2
HgO
Hg O2 2 1
2 Hg, 2 O
2 Hg, 2 O