Chapter 6. Chemical Reactions: Classification and Mass Relationships. Balancing Chemical Equations. Alphabet – elemental symbols Words – chemical formulas Sentences – chemical equations (chemical reactions) reactants products limestone quicklime + gas
Chemical Reactions: Classification and Mass Relationships
limestone quicklime + gas
Calcium carbonate calcium oxide + carbon dioxide
CaCO3(s) CaO(s) + CO2(g)
2 C4H10(g) + 13 O2(g) → 8 CO2(g) + 10 H2O (g)
8 molecule of CO2(g) and 10 molecules of H2O(g)
Fe2O3(s) + CO(g) → Fe(s) + CO2(g)
AX + BY AY + BX
Loss (of electrons)
Gain (of electrons)
1. An atom in its elemental state has an oxidation number of zero.
2. An atom in a monatomic ion has an oxidation number identical to its charge.
3. An atom in a polyatomic ion or in a molecular compound usually has the same oxidation number it would have if it were a monatomic ion.
4. The sum of the oxidation numbers must be zero for a neutral compound and must be equal to the net charge for a polyatomic ion.
? = 0 – 2(+1) – 4(–2) = +6
? = –1 – 4(–2) = +7