WARM UP Write a balanced chemical equation for the reaction between hydrogen gas (H2) and carbon monoxide gas (CO) to yield liquid methanol (CH3OH), including states of matter.

Types of Reactions

Precipitation Reactions (aq) reactants create (s) product (s) is insoluble precipitate Table 4.2 Pb(NO3)2(aq) + 2KI(aq)  PbI2(s) + 2KNO3(aq)

Precipitation Reactions Molecular equation The “normal” equation Pb(NO3)2(aq) + 2KI(aq)  PbI2(s) + 2KNO3(aq)

Precipitation Reactions Ionic equation Write ionic(aq) as + and – ions Pb2+(aq) + 2NO3-(aq) + 2K+(aq) + 2I-(aq)  PbI2(s) + 2K+(aq) + 2NO3-(aq)

Precipitation Reactions Net ionic equation Cancel ions that are the same on both sides of equation Pb2+(aq) + 2I-(aq)  PbI2(s)

Oxidation-Reduction Reactions Transfers of electrons Alter charges of atoms in reactants and products Oxidation number Like ionic charge = charge of ion = 0 in free elements = 0 in full compounds in compounds, H = +1 O = -2 F = -1

Oxidation-Reduction Reactions Loss of e- Becoming more + from reactants to products Half-Reaction H2 + Cl2  2 HCl +1

Oxidation-Reduction Reactions Gain of e- Becoming more – from reactants to products Half-Reaction H2 + Cl2  2 HCl -1

WRAP UP Explain how you can identify a precipitation reaction from an equation. Explain how you can identify an oxidation-reduction reaction from an equation.