Chemistry notes
9.3 – The Acidic Environment:
Δ. Construct word and balanced formulae equations of all chemical reactions as they are encountered in this module:
NOTE: In chemistry, [x] means “concentration of x” in moles per litre (mol/L).
EG: [H3O+] means “concentration of H3O+ ions” in mol/L.
BASIC reactions to remember:
Acid reactions: acid + base salt + water acid + metal salt + hydrogen gas acid + carbonate carbon dioxide gas + salt + water
Formation of hydronium:
H+ + H2O H3O+
Reactions of various oxides with water:
Non-metal (acidic) oxides:
CO2 (g) + H2O (l) H2CO3 (aq) (carbonic acid)
SO2 (g) + H2O (l) H2SO3 (aq) (sulfurous acid)
2NO2 (g) + H2O (l) HNO3 (aq) + HNO2 (aq) (nitric and nitrous acid)
P2O5 (g) + H2O (l) 2H3PO4 (aq) (phosphoric acid)
Metal (basic) oxides:
K2O (s) + H2O (l) 2KOH (aq) (potassium hydroxide)
Na2O (s) + H2O (l) 2NaOH (aq) (sodium hydroxide)
MgO (s) + H2O (l) Mg(OH)2 (aq) (magnesium hydroxide)
Various EQUILIBRIUM reactions:
Formation of carbonic acid: CO2 (g) + H2O (l) H2CO3 (aq)
Copper complex-ions: Cu(H2O)42+ (aq) + 4Cl־(aq) CuCl42־(aq) + 4H2O (l)
Decomposition of dinitrogen tetroxide: N2O4 (g) 2NO2 (g)
Decomposition of calcium carbonate: CaCO3 (s) CaO (s) + CO2 (g)
Non-Arrhenius acid/base reaction:
Gaseous hydrogen chloride and ammonia react:
HCl (g) + NH3 (g) NH4Cl (s)
IONISATION of strong and weak acids:
Hydrochloric: HCl (g) + H2O (l) H3O+ (aq) + Cl־ (aq)
Nitric: HNO3 (l) + H2O (l) H3O+ (aq) + NO3-
Sulfuric: H2SO4 (l) + 2H2O (l) 2H3O+ (aq) + SO42־
Ethanoic: CH3COOH (s) + H2O (l) H3O+ (aq) + CH3COO־ (aq)
Sources of sulfur and nitrogen oxides in the atmosphere:
Sulfur Oxides:
Organic decomposition: 2H2S (g) + 3O2 (g) 2SO2 (g) + 2H2O (l)
Burning high-sulfur coals: S (s) + O2 (g) SO2 (g)
Smelting metal sulfides: 2PbS (s) + 3O2 (g) 2PbO (s) + 2SO2
Nitrogen Oxides:
Lightning: N2 (g) + O2 (g) 2NO (g)
Oxidation of nitrogen monoxide: 2NO (g) + O2 (g) NO2 (g)
Amphiprotic
Δ. Construct word and balanced formulae equations of all chemical reactions as they are encountered in this module:
NOTE: In chemistry, [x] means “concentration of x” in moles per litre (mol/L).
EG: [H3O+] means “concentration of H3O+ ions” in mol/L.
BASIC reactions to remember:
Acid reactions: acid + base salt + water acid + metal salt + hydrogen gas acid + carbonate carbon dioxide gas + salt + water
Formation of hydronium:
H+ + H2O H3O+
Reactions of various oxides with water:
Non-metal (acidic) oxides:
CO2 (g) + H2O (l) H2CO3 (aq) (carbonic acid)
SO2 (g) + H2O (l) H2SO3 (aq) (sulfurous acid)
2NO2 (g) + H2O (l) HNO3 (aq) + HNO2 (aq) (nitric and nitrous acid)
P2O5 (g) + H2O (l) 2H3PO4 (aq) (phosphoric acid)
Metal (basic) oxides:
K2O (s) + H2O (l) 2KOH (aq) (potassium hydroxide)
Na2O (s) + H2O (l) 2NaOH (aq) (sodium hydroxide)
MgO (s) + H2O (l) Mg(OH)2 (aq) (magnesium hydroxide)
Various EQUILIBRIUM reactions:
Formation of carbonic acid: CO2 (g) + H2O (l) H2CO3 (aq)
Copper complex-ions: Cu(H2O)42+ (aq) + 4Cl־(aq) CuCl42־(aq) + 4H2O (l)
Decomposition of dinitrogen tetroxide: N2O4 (g) 2NO2 (g)
Decomposition of calcium carbonate: CaCO3 (s) CaO (s) + CO2 (g)
Non-Arrhenius acid/base reaction:
Gaseous hydrogen chloride and ammonia react:
HCl (g) + NH3 (g) NH4Cl (s)
IONISATION of strong and weak acids:
Hydrochloric: HCl (g) + H2O (l) H3O+ (aq) + Cl־ (aq)
Nitric: HNO3 (l) + H2O (l) H3O+ (aq) + NO3-
Sulfuric: H2SO4 (l) + 2H2O (l) 2H3O+ (aq) + SO42־
Ethanoic: CH3COOH (s) + H2O (l) H3O+ (aq) + CH3COO־ (aq)
Sources of sulfur and nitrogen oxides in the atmosphere:
Sulfur Oxides:
Organic decomposition: 2H2S (g) + 3O2 (g) 2SO2 (g) + 2H2O (l)
Burning high-sulfur coals: S (s) + O2 (g) SO2 (g)
Smelting metal sulfides: 2PbS (s) + 3O2 (g) 2PbO (s) + 2SO2
Nitrogen Oxides:
Lightning: N2 (g) + O2 (g) 2NO (g)
Oxidation of nitrogen monoxide: 2NO (g) + O2 (g) NO2 (g)
Amphiprotic