4.3 Oxidation Reduction Reactions

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Oxidation-Reduction Reaction (Redox Reactions) - A reaction in which the oxidation states (charges) of atoms change from reactants to products

2Na(s) + Cl2(g) ➔ 2NaCl(s)

Oxidation is the loss of electrons

Reduction is the gain of electrons





1 Atoms in their elemental form are in the zero oxidation state.
2 Monatomic ions in ionic compounds get their typical ionic charge.
3 Atoms in Molecular Compounds and Polyatomic Ions

Oxygen        -2 except in peroxide O22-

Hydrogen     +1 (when bonded with any nonmetals)

Fluorine        -1 always

Halogens      -1 except when bonded to Oxygen

4 The oxidation numbers sum to zero for a compound or to the overall charge of a polyatomic ion.

Determine oxidation states for all elements in the following:

Na                                   O2                                   NaCl                                   NaHCO3



CO2                                 H2O2                               SO42-

Which of the following are oxidation-reduction reactions?

2Mg(s) + O2(g) ➔ 2MgO(s)


CaCO3(s) ➔ CaO(s) + CO2(g)


AgNO3(aq) + HCl(aq) ➔ AgCl(s) + HNO3(aq)


 2AgNO3(aq) + Cu(s) ➔ Cu(NO3)2 + 2Ag(s)

Single Displacement Reactions

Which of the following reactions are spontaneous?

Mg(s) + 2HCl(aq) ➔ MgCl2(aq) + H2(g)


Cu(s) + Zn(NO3)2(aq) ➔ Cu(NO3)2(aq) + Zn(s)


 Mn(s) + Ni2+(aq) ➔ Mn2+(aq) + Ni(s)

single displacement reactions