2. This is a chemical recipe for
the decomposition of water
by electrolysis.
reactants
products
What did John Dalton in 1808 have to say about chemical reactions?
Is this true for the decomposition of water by electrolysis?
2. Atoms are conserved in a chemical reaction.
In other words, atoms are not created nor destroyed in chemical reaction.
1. Chemical reactions involve just the simple rearrangement of atoms.

3. 1. Chemical reactions involve just the simple rearrangement of atoms.
2. Atoms are conserved in a chemical reaction.
In other words, atoms are not created nor destroyed in chemical reaction.
This ture for the above decomposition of water by electrolysis.
Let’s see if John Dalton had assumed correctly.
4 hydrogen atoms
2 oxygen atoms

4. Cl – Fe 2+ Fe(s) + Cl2(g) FeCl2 (s) Feo Fe 2+ + 2e- Cl2o + 2e- 2Cl –
Combination - Synthesis (the REDOX process defined)
Fe 2+
Cl –
iron (II) chloride
chlorine gas
iron metal
forms>
plus 1
Fe(s) Cl2(g) FeCl2 (s) 1 1
Analyzing the half reactions
Feo Fe e-
Oxidation
OIL 1
Cl2o e Cl –
Reduction
RIG

5. Cl – Fe 2+ Fe(s) + Cl2(g) FeCl2 (s) Feo Fe 2+ + 2e- Cl2o + 2e- 2Cl –1
Combination - Synthesis (the REDOX process defined)
Analyzing the half reactions
Fe 2+
Cl –
iron (II) chloride
chlorine gas
iron metal
forms
the electrons on the reactant side cancel the electrons on the product side 1
Feo Fe e-
Oxidation
OIL 1 1 1
Cl2o e Cl –
Reduction
RIG
combining both half reactions
1 Fe(s) Cl2(g) FeCl2 (s)

6. (s) (s) (g) What reactant was oxidized? What reactant was reduced?
Mgo lost electrons
O2O
Mg O
Mg 2+
O 2–
(s)
magnesium oxide
solid ionic salt
(s)
magnesium metal
solid
Oxygen gained electrons
(g)
oxygen
gas

7. 4 3 2 (s) (g) What reactant was oxidized? What reactant was reduced?
Fe 3+
O 2–
Fe O
Iron metal lost electrons
O2O
Oxygen gained electrons 4 3 2
(s)
iron metal
solid
(g)
oxygen
gas
iron (III) oxide
solid TM ionic salt

8. CH4O + O2 CO2 + H2O CH4O + O2 CO2 + H2O C2H6O + O2 CO2 + H2O
Combustion of methanol, CH4O
Don’t leave as a fraction, multiply through by 2
combustion
CH4O O CO H2O 2 4 3 2x 3 __ 2 1
CH4O O CO H2O 1 2 o
Combustion of ethanol, C2H4O 1
C2H6O O CO H2O 3 2 3
Combustion of formaldehyde, CH2O
C 4+
O 2– 1
CH2O O CO H2O 1 1 1
What reactant was oxidized?
What reactant was reduced?

9. Now balance the combustion of glucose (blood sugar)1 6 ? 6 6
1 • O • 1O
Always balance oxygens last
1•O ? • O2 = 18
= 18
? • 2 = 18
Now solve for “?”
? • 2 = 12 -6
? = 6 2
Divide each side by 2
Substract 6 from each side

10. CO2 + H2O C6H12O6 + O2 Combination - Synthesis - PHOTOSYNTHESIS 6 6 1
chlorophyll
catalyst 6 6 1 6