Types of Chemical Reactions

Combustion

• the "burning" of compounds in $\ce{O_{2(g)}}$

$$\ce {2C4H10{(g)} + 13O2 (g) -> 8CO2 (g) + 10H2O(l)}$$

Notes:

1. The combustion of hydrocarbons only gives $\ce{CO_2}$ and $\ce{H_2O}$
2. commonly used in compound identification

Precipitation

• reactions that produce a sparingly soluble product called a precipitate

$$\ce{NaCl(aq) + AgNO3 (aq) -> AgCl(s) + NaNO3 (aq)}$$

• called a molecular equation; shown as molecules

$$\ce{Na+ (aq) + Cl- (aq) + Ag+ (aq) + NO3 - (aq) -> AgCl(s) + Na+ (aq) + NO3- (aq)}$$

• called an ionic equation; shown as ions, if possible; more realistic

$$\ce {Cl- (aq) + Ag+ (aq) -> AgCl(s)}$$

• called a net ionic equation; spectator ions cancelled

Notes:

1. we will discuss precipitation reactions in aqueous media only
2. know the rules to identify which products are soluble and which are precipitates in water

Acid / Base

• proton transfer reactions; transfer of $\ce{H+}$

$$\ce {HCl(aq) + NH3 (aq) -> NH4+ (aq) + Cl- (aq)}$$

Brønsted-Lowry definition:

• acid ($\ce{HCl}$): proton donor

• base ($\ce{NH3}$): proton acceptor

• Strong acids and bases: completely ionize in water

• Weak acids and bases: partially ionize in water

Notes:

1. must know the common strong acids and bases in aqueous media; everything else is weak

Redox

• electron transfer reactions

$$\ce{Cu(s) + 2AgNO3 (aq) -> 2Ag(s) + Cu(NO3)2 (aq)}$$

• convert to an ionic equation

$$\ce{Cu(s) + 2Ag+(aq) + 2NO3- (aq) -> 2Ag(s) + Cu2+(aq) + 2NO3- (aq)}$$

• convert to a net ionic equation

$$\ce{Cu(s) + 2Ag+ (aq) -> 2Ag(s) + Cu2+(aq)}$$

• consider this process as two half-reactions
  • $\ce{Cu(s) Cu2+(aq) + 2e-}$ involves the loss of $\ce{e-}$ : oxidation
  • $\ce{2Ag+ (aq) + 2e- -> 2Ag(s)}$ involves the gain of $\ce{e-}$: reduction