2 Equations

• General reaction:

  Substance + oxygen -> oxides

  Examples:

  2 Mg + O2 -> 2 MgO

  2 H2S + 3 O2 -> 2 SO2

  C3H8 + 5 O2 -> 3 CO2 + 4 H2O
• General reaction:

  metal + water -> metal hydroxide + hydrogen

  Example:

  2 Na + 2 H2O -> 2 NaOH + H2
• General reaction:

  Metal + acid -> salt + hydrogen

  Examples:

  Mg + 2HCl -> MgCl2 + H2
• General reaction:

  oxide + acid -> salt + water

  Example:

  MgO + 2 HNO3 -> Mg(NO3)2 + H2O
• General reaction:

  Hydroxide + acid -> salt + water

  Example:

  2 NaOH + H2SO4 -> Na2SO4 + H2O
• General reaction:

  Carbonate + acid -> salt + water + carbon dioxide

  Examples:

  CuCO3 + 2 HCl -> CuCl2 + H2O + CO2
• General reaction:

  Hydrogencarbonate + acid -> salt + water + carbon dioxide

  Examples:

  KHCO3 + HCl -> KCl + H2O + CO2
• General reaction:

  Ammonia + acid -> ammonium salt

  Examples:

  NH3 + HCl -> NH4Cl
• General reaction:

  Metal carbonate -> metal oxide + carbon dioxide (on heating)

  Examples:

  CaCO3 -> CaO + CO2
• When an ionic substance dissolves in water, the positive and negative ions separate and become hydrated (they interact with water molecules rather than each other). For example, a solution of sodium chloride could also be described as a mixture of hydrated sodium ions and hydrated chloride ions in water
• In reactions involving ionic compounds dissolved in water, some of the ions may not be Involved in the reaction. These are called spectator ions. For such reactions we can write an ionic equation that only shows the species that are involved in the reaction.
• Common ionic equation

  Acid + hydroxide

  Example

  H+(aq) + OH- (aq) -> H2O(l)
• Common ionic equations

  Acid + carbonate

  Example

  2 H+(aq) + CO3²-(aq) -> H2O(l) + CO2(g)
• Common ionic equations

  Acid + hydrogencarbonate

  Examples

  H+(aq) + HCO3-(aq) -> H2O(l) + CO2(g)
• Common ionic equations

  Acid + ammonia

  Example

  H+(aq) + NH3(aq) -> NH4+(aq)
• Stoichiometry - balance the equation
• We can use the common ionic equations to work put the ratio in which acids react without writing an equation. For example in the reaction of H2SO4 (aq) with NaOH(aq) we know that one lot of H2SO4 contains two lots of H+ ions. As H+ ions react with OH- ions in the ration 1:1 [H+(aq) + OH-(aq) -> H2O(l)] we knkw that we need two lots of NaOH tk provide two lots of OH ions react with the two lots of H+ ions. Therefore one lot of H2SO4 reacts with two lots of NaOH i.e the reacting ratio of H2SO4:NaOh = 1:2