Chemistry Formulas

Periodic Table & Bonding

Sodium with water

2 Na(s)+2 HX2O(l)→2 NaOH(aq)+HX2(g)\ce{2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2(g)}

Sodium with oxygen

4 Na(s)+OX2(g)→2 NaX2O(s)\ce{4Na(s) + O2(g) -> 2Na2O(s)}

Magnesium with oxygen

2 Mg(s)+OX2(g)→2 MgO(s)\ce{2Mg(s) + O2(g) -> 2MgO(s)}

Magnesium with HCl

Mg(s)+2 HCl(aq)→MgClX2(aq)+HX2(g)\ce{Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g)}

Iron with oxygen

3 Fe(s)+2 OX2(g)→FeX3OX4(s)\ce{3Fe(s) + 2O2(g) -> Fe3O4(s)}

Potassium with water

2 K(s)+2 HX2O(l)→2 KOH(aq)+HX2(g)\ce{2K(s) + 2H2O(l) -> 2KOH(aq) + H2(g)}

Calcium with water

Ca(s)+2 HX2O(l)→Ca(OH)X2(aq)+HX2(g)\ce{Ca(s) + 2H2O(l) -> Ca(OH)2(aq) + H2(g)}

Iron with chlorine

2 Fe(s)+3 ClX2(g)→2 FeClX3(s)\ce{2Fe(s) + 3Cl2(g) -> 2FeCl3(s)}

Hydrogen with chlorine

HX2(g)+ClX2(g)→2 HCl(g)\ce{H2(g) + Cl2(g) -> 2HCl(g)}

Sulfur with oxygen

S(s)+OX2(g)→SOX2(g)\ce{S(s) + O2(g) -> SO2(g)}

Iron with sulfur

Fe(s)+S(s)→heatFeS(s)\ce{Fe(s) + S(s) ->[heat] FeS(s)}

Copper with oxygen (heated)

2 Cu(s)+OX2(g)→heat2 CuO(s)\ce{2Cu(s) + O2(g) ->[heat] 2CuO(s)}

Acids, Bases & Salts

Neutralisation: HCl + NaOH

HCl(aq)+NaOH(aq)→NaCl(aq)+HX2O(l)\ce{HCl(aq) + NaOH(aq) -> NaCl(aq) + H2O(l)}

Neutralisation: H₂SO₄ + NaOH

HX2SOX4(aq)+2 NaOH(aq)→NaX2SOX4(aq)+2 HX2O(l)\ce{H2SO4(aq) + 2NaOH(aq) -> Na2SO4(aq) + 2H2O(l)}

Acid + carbonate: HCl + CaCO3

2 HCl(aq)+CaCOX3(s)→CaClX2(aq)+HX2O(l)+COX2(g)\ce{2HCl(aq) + CaCO3(s) -> CaCl2(aq) + H2O(l) + CO2(g)}

Acid + metal: HCl + Fe

2 HCl(aq)+Fe(s)→FeClX2(aq)+HX2(g)\ce{2HCl(aq) + Fe(s) -> FeCl2(aq) + H2(g)}

Precipitation: AgNO₃ + NaCl

AgNOX3(aq)+NaCl(aq)→AgCl(s)v+NaNOX3(aq)\ce{AgNO3(aq) + NaCl(aq) -> AgCl(s)v + NaNO3(aq)}

Precipitation: Pb(NO₃)₂ + KI

Pb(NOX3)X2(aq)+2 KI(aq)→PbIX2(s)v+2 KNOX3(aq)\ce{Pb(NO3)2(aq) + 2KI(aq) -> PbI2(s)v + 2KNO3(aq)}

Acid + metal: H₂SO₄ + Fe

HX2SOX4(aq)+Fe(s)→FeSOX4(aq)+HX2(g)\ce{H2SO4(aq) + Fe(s) -> FeSO4(aq) + H2(g)}

Neutralisation: H₂SO₄ + KOH

HX2SOX4(aq)+2 KOH(aq)→KX2SOX4(aq)+2 HX2O(l)\ce{H2SO4(aq) + 2KOH(aq) -> K2SO4(aq) + 2H2O(l)}

Acid + metal oxide: HCl + MgO

2 HCl(aq)+MgO(s)→MgClX2(aq)+HX2O(l)\ce{2HCl(aq) + MgO(s) -> MgCl2(aq) + H2O(l)}

Acid + metal hydroxide: H₂SO₄ + Ca(OH)₂

HX2SOX4(aq)+Ca(OH)X2(aq)→CaSOX4(s)v+2 HX2O(l)\ce{H2SO4(aq) + Ca(OH)2(aq) -> CaSO4(s)v + 2H2O(l)}

Acid + hydrogen carbonate: HCl + NaHCO₃

HCl(aq)+NaHCOX3(s)→NaCl(aq)+HX2O(l)+COX2(g)\ce{HCl(aq) + NaHCO3(s) -> NaCl(aq) + H2O(l) + CO2(g)}

Precipitation: Pb(NO₃)₂ + NaCl

Pb(NOX3)X2(aq)+2 NaCl(aq)→PbClX2(s)v+2 NaNOX3(aq)\ce{Pb(NO3)2(aq) + 2NaCl(aq) -> PbCl2(s)v + 2NaNO3(aq)}

Precipitation: BaCl₂ + H₂SO₄

BaClX2(aq)+HX2SOX4(aq)→BaSOX4(s)v+2 HCl(aq)\ce{BaCl2(aq) + H2SO4(aq) -> BaSO4(s)v + 2HCl(aq)}

Precipitation: AgNO₃ + NaBr

AgNOX3(aq)+NaBr(aq)→AgBr(s)v+NaNOX3(aq)\ce{AgNO3(aq) + NaBr(aq) -> AgBr(s)v + NaNO3(aq)}

Precipitation: AgNO₃ + KI

AgNOX3(aq)+KI(aq)→AgI(s)v+KNOX3(aq)\ce{AgNO3(aq) + KI(aq) -> AgI(s)v + KNO3(aq)}

Precipitation: CaCl₂ + Na₂CO₃

CaClX2(aq)+NaX2COX3(aq)→CaCOX3(s)v+2 NaCl(aq)\ce{CaCl2(aq) + Na2CO3(aq) -> CaCO3(s)v + 2NaCl(aq)}

Ammonia + HCl

NHX3(g)+HCl(g)→NHX4Cl(s)\ce{NH3(g) + HCl(g) -> NH4Cl(s)}

Ethanoic acid + magnesium

2 CHX3COOH(aq)+Mg(s)→(CHX3COO)X2Mg(aq)+HX2(g)\ce{2CH3COOH(aq) + Mg(s) -> (CH3COO)2Mg(aq) + H2(g)}

Ethanoic acid + Na₂CO₃

2 CHX3COOH(aq)+NaX2COX3(s)→2 CHX3COONa(aq)+HX2O(l)+COX2(g)\ce{2CH3COOH(aq) + Na2CO3(s) -> 2CH3COONa(aq) + H2O(l) + CO2(g)}

Ethanoic acid + NaOH

CHX3COOH(aq)+NaOH(aq)→CHX3COONa(aq)+HX2O(l)\ce{CH3COOH(aq) + NaOH(aq) -> CH3COONa(aq) + H2O(l)}

Removing temporary hardness (boiling)

Ca(HCOX3)X2(aq)→heatCaCOX3(s)v+HX2O(l)+COX2(g)\ce{Ca(HCO3)2(aq) ->[heat] CaCO3(s)v + H2O(l) + CO2(g)}

Removing permanent hardness (Na₂CO₃)

CaSOX4(aq)+NaX2COX3(aq)→CaCOX3(s)v+NaX2SOX4(aq)\ce{CaSO4(aq) + Na2CO3(aq) -> CaCO3(s)v + Na2SO4(aq)}

Oxidation-Reduction

Combustion of carbon

C(s)+OX2(g)→COX2(g)\ce{C(s) + O2(g) -> CO2(g)}

Combustion of hydrogen

2 HX2(g)+OX2(g)→2 HX2O(l)\ce{2H2(g) + O2(g) -> 2H2O(l)}

Combustion of methane

CHX4(g)+2 OX2(g)→COX2(g)+2 HX2O(l)\ce{CH4(g) + 2O2(g) -> CO2(g) + 2H2O(l)}

Combustion of ethane

2 CX2HX6(g)+7 OX2(g)→4 COX2(g)+6 HX2O(l)\ce{2C2H6(g) + 7O2(g) -> 4CO2(g) + 6H2O(l)}

Combustion of ethanol

CX2HX5OH(l)+3 OX2(g)→2 COX2(g)+3 HX2O(l)\ce{C2H5OH(l) + 3O2(g) -> 2CO2(g) + 3H2O(l)}

Halogen displacement: Cl₂ + NaBr

ClX2(aq)+2 NaBr(aq)→BrX2(aq)+2 NaCl(aq)\ce{Cl2(aq) + 2NaBr(aq) -> Br2(aq) + 2NaCl(aq)}

Metal displacement: Fe + CuSO₄

Fe(s)+CuSOX4(aq)→FeSOX4(aq)+Cu(s)\ce{Fe(s) + CuSO4(aq) -> FeSO4(aq) + Cu(s)}

Halogen displacement: Cl₂ + KBr

ClX2(aq)+2 KBr(aq)→BrX2(aq)+2 KCl(aq)\ce{Cl2(aq) + 2KBr(aq) -> Br2(aq) + 2KCl(aq)}

Halogen displacement: Br₂ + KI

BrX2(aq)+2 KI(aq)→IX2(aq)+2 KBr(aq)\ce{Br2(aq) + 2KI(aq) -> I2(aq) + 2KBr(aq)}

Metal displacement: Zn + FeSO₄

Zn(s)+FeSOX4(aq)→ZnSOX4(aq)+Fe(s)\ce{Zn(s) + FeSO4(aq) -> ZnSO4(aq) + Fe(s)}

Metal displacement: Mg + FeCl₃

3 Mg(s)+2 FeClX3(aq)→3 MgClX2(aq)+2 Fe(s)\ce{3Mg(s) + 2FeCl3(aq) -> 3MgCl2(aq) + 2Fe(s)}

Rusting of iron

4 Fe(s)+3 OX2(g)+2x HX2O(l)→2 FeX2OX3 ⋅ x HX2O(s)\ce{4Fe(s) + 3O2(g) + 2xH2O(l) -> 2Fe2O3.xH2O(s)}

Carbon reduces iron oxide

2 FeX2OX3(s)+3 C(s)→heat4 Fe(s)+3 COX2(g)\ce{2Fe2O3(s) + 3C(s) ->[heat] 4Fe(s) + 3CO2(g)}

Carbon monoxide reduces iron oxide

FeX2OX3(s)+3 CO(g)→heat2 Fe(s)+3 COX2(g)\ce{Fe2O3(s) + 3CO(g) ->[heat] 2Fe(s) + 3CO2(g)}

Hydrogen reduces copper oxide

CuO(s)+HX2(g)→heatCu(s)+HX2O(l)\ce{CuO(s) + H2(g) ->[heat] Cu(s) + H2O(l)}

Iron with steam

3 Fe(s)+4 HX2O(g)→heatFeX3OX4(s)+4 HX2(g)\ce{3Fe(s) + 4H2O(g) ->[heat] Fe3O4(s) + 4H2(g)}

Chlorine with water

ClX2(g)+HX2O(l)→HCl(aq)+HClO(aq)\ce{Cl2(g) + H2O(l) -> HCl(aq) + HClO(aq)}

Chlorine with alkali

ClX2(g)+2 NaOH(aq)→NaCl(aq)+NaClO(aq)+HX2O(l)\ce{Cl2(g) + 2NaOH(aq) -> NaCl(aq) + NaClO(aq) + H2O(l)}

Organic Chemistry

Addition: ethene + bromine

CX2HX4(g)+BrX2(aq)→CX2HX4BrX2(l)\ce{C2H4(g) + Br2(aq) -> C2H4Br2(l)}

Addition: ethene + water

CX2HX4(g)+HX2O(l)→HX2SOX4,heatCX2HX5OH(l)\ce{C2H4(g) + H2O(l) ->[H2SO4, heat] C2H5OH(l)}

Esterification: ethanol + ethanoic acid

CX2HX5OH(l)+CHX3COOH(l)⇌CHX3COOCX2HX5(l)+HX2O(l)\ce{C2H5OH(l) + CH3COOH(l) <=> CH3COOC2H5(l) + H2O(l)}

Substitution: methane + chlorine

CHX4(g)+ClX2(g)→UV lightCHX3Cl(g)+HCl(g)\ce{CH4(g) + Cl2(g) ->[UV light] CH3Cl(g) + HCl(g)}

Polymerisation: ethene

n CX2HX4→(CX2HX4)Xn\ce{n C2H4 -> (C2H4)_n}

Combustion of propane

CX3HX8(g)+5 OX2(g)→3 COX2(g)+4 HX2O(l)\ce{C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O(l)}

Complete combustion of butane

2 CX4HX10(g)+13 OX2(g)→8 COX2(g)+10 HX2O(l)\ce{2C4H10(g) + 13O2(g) -> 8CO2(g) + 10H2O(l)}

Substitution: ethane + chlorine

CX2HX6(g)+ClX2(g)→UVCX2HX5Cl(g)+HCl(g)\ce{C2H6(g) + Cl2(g) ->[UV] C2H5Cl(g) + HCl(g)}

Substitution: propane + bromine

CX3HX8(g)+BrX2(g)→UVCX3HX7Br(g)+HBr(g)\ce{C3H8(g) + Br2(g) ->[UV] C3H7Br(g) + HBr(g)}

Addition: ethene + hydrogen

CX2HX4(g)+HX2(g)→Ni,heatCX2HX6(g)\ce{C2H4(g) + H2(g) ->[Ni, heat] C2H6(g)}

Addition: ethene + HCl

CX2HX4(g)+HCl(g)→CX2HX5Cl(l)\ce{C2H4(g) + HCl(g) -> C2H5Cl(l)}

Addition: ethene + HBr

CX2HX4(g)+HBr(g)→CX2HX5Br(l)\ce{C2H4(g) + HBr(g) -> C2H5Br(l)}

Addition: propene + bromine

CX3HX6(g)+BrX2(aq)→CX3HX6BrX2(l)\ce{C3H6(g) + Br2(aq) -> C3H6Br2(l)}

Addition: propene + water

CX3HX6(g)+HX2O(l)→HX2SOX4CX3HX7OH(l)\ce{C3H6(g) + H2O(l) ->[H2SO4] C3H7OH(l)}

Dehydration of ethanol to ethene

CX2HX5OH(l)→HX2SOX4,heatCX2HX4(g)+HX2O(l)\ce{C2H5OH(l) ->[H2SO4, heat] C2H4(g) + H2O(l)}

Oxidation: ethanol to ethanal

CX2HX5OH(l)+[O]→CX2HX4O(l)+HX2O(l)\ce{C2H5OH(l) + [O] -> C2H4O(l) + H2O(l)}

Oxidation: ethanol to ethanoic acid

CX2HX5OH(l)+2 [O]→CHX3COOH(l)+HX2O(l)\ce{C2H5OH(l) + 2[O] -> CH3COOH(l) + H2O(l)}

Esterification: methanol + ethanoic acid

CHX3OH(l)+CHX3COOH(l)⇌CHX3COOCHX3(l)+HX2O(l)\ce{CH3OH(l) + CH3COOH(l) <=> CH3COOCH3(l) + H2O(l)}

Esterification: propanol + ethanoic acid

CX3HX7OH(l)+CHX3COOH(l)⇌CHX3COOCX3HX7(l)+HX2O(l)\ce{C3H7OH(l) + CH3COOH(l) <=> CH3COOC3H7(l) + H2O(l)}

Hydrolysis of ethyl ethanoate

CHX3COOCX2HX5(l)+HX2O(l)⇌CHX3COOH(aq)+CX2HX5OH(aq)\ce{CH3COOC2H5(l) + H2O(l) <=> CH3COOH(aq) + C2H5OH(aq)}

Saponification of ethyl ethanoate

CHX3COOCX2HX5(l)+NaOH(aq)→CHX3COONa(aq)+CX2HX5OH(aq)\ce{CH3COOC2H5(l) + NaOH(aq) -> CH3COONa(aq) + C2H5OH(aq)}

Fermentation of glucose

CX6HX12OX6(aq)→yeast2 CX2HX5OH(l)+2 COX2(g)\ce{C6H12O6(aq) ->[yeast] 2C2H5OH(l) + 2CO2(g)}

Polymerisation of propene

n CX3HX6→(CX3HX6)Xn\ce{n C3H6 -> (C3H6)_n}

Polymerisation of chloroethene (vinyl chloride)

n CX2HX3Cl→(CX2HX3Cl)Xn\ce{n C2H3Cl -> (C2H3Cl)_n}

Ethanol + sodium

2 CX2HX5OH(l)+2 Na(s)→2 CX2HX5ONa(l)+HX2(g)\ce{2C2H5OH(l) + 2Na(s) -> 2C2H5ONa(l) + H2(g)}

Stoichiometry & Moles

Combustion of butane

2 CX4HX10(g)+13 OX2(g)→8 COX2(g)+10 HX2O(l)\ce{2C4H10(g) + 13O2(g) -> 8CO2(g) + 10H2O(l)}

Thermal decomposition: CaCO3

CaCOX3(s)→heatCaO(s)+COX2(g)\ce{CaCO3(s) ->[heat] CaO(s) + CO2(g)}

Thermal decomposition: Pb(NO₃)₂

2 Pb(NOX3)X2(s)→heat2 PbO(s)+4 NOX2(g)+OX2(g)\ce{2Pb(NO3)2(s) ->[heat] 2PbO(s) + 4NO2(g) + O2(g)}

Thermal decomposition: NaHCO3

2 NaHCOX3(s)→heatNaX2COX3(s)+HX2O(l)+COX2(g)\ce{2NaHCO3(s) ->[heat] Na2CO3(s) + H2O(l) + CO2(g)}

Combustion of propane (molar)

CX3HX8(g)+5 OX2(g)→3 COX2(g)+4 HX2O(l)\ce{C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O(l)}

Limiting reagent: Na + Cl₂

2 Na(s)+ClX2(g)→2 NaCl(s)\ce{2Na(s) + Cl2(g) -> 2NaCl(s)}

Limiting reagent: Fe + S

Fe(s)+S(s)→FeS(s)\ce{Fe(s) + S(s) -> FeS(s)}

Qualitative Analysis

Test for carbonate: CO₃²⁻ + H⁺

COX3X2−(aq)+2 HX+(aq)→HX2O(l)+COX2(g)↑\ce{CO3^{2-}(aq) + 2H^+(aq) -> H2O(l) + CO2(g) ^}

Test for sulfate: Ba²⁺ + SO₄²⁻

BaX2+(aq)+SOX4X2−(aq)→BaSOX4(s)↓\ce{Ba^{2+}(aq) + SO4^{2-}(aq) -> BaSO4(s) v}

Test for sulfite: SO₃²⁻ + H⁺

SOX3X2−(aq)+2 HX+(aq)→SOX2(g)↑+HX2O(l)\ce{SO3^{2-}(aq) + 2H^+(aq) -> SO2(g) ^ + H2O(l)}

Test for halides: Ag⁺ + halide

AgX+(aq)+ClX−(aq)→AgCl(s)↓\ce{Ag^+(aq) + Cl^-(aq) -> AgCl(s) v}

Test for NH₄⁺: OH⁻ + heat

NHX4X++OHX−→heatNHX3↑+HX2O\ce{NH4^+ + OH^- ->[heat] NH3 ^ + H2O}

Test for Fe²⁺: NaOH

FeX2+(aq)+2 OHX−(aq)→Fe(OH)X2(s)↓\ce{Fe^{2+}(aq) + 2OH^-(aq) -> Fe(OH)2(s) v}

Test for Fe³⁺: NaOH

FeX3+(aq)+3 OHX−(aq)→Fe(OH)X3(s)↓\ce{Fe^{3+}(aq) + 3OH^-(aq) -> Fe(OH)3(s) v}

Test for Cu²⁺: NaOH

CuX2+(aq)+2 OHX−(aq)→Cu(OH)X2(s)↓\ce{Cu^{2+}(aq) + 2OH^-(aq) -> Cu(OH)2(s) v}

Test for Cu²⁺: NH₃ (excess)

CuX2+(aq)+4 NHX3(aq)→[Cu(NHX3)X4]X2+(aq)\ce{Cu^{2+}(aq) + 4NH3(aq) -> [Cu(NH3)4]^{2+}(aq)}

Test for Zn²⁺: NaOH (excess)

ZnX2+(aq)+2 OHX−(aq)→Zn(OH)X2(s)↓\ce{Zn^{2+}(aq) + 2OH^-(aq) -> Zn(OH)2(s) v}

Test for Al³⁺: NaOH (excess)

AlX3+(aq)+3 OHX−(aq)→Al(OH)X3(s)↓\ce{Al^{3+}(aq) + 3OH^-(aq) -> Al(OH)3(s) v}

Test for Ca²⁺: NaOH

CaX2+(aq)+2 OHX−(aq)→Ca(OH)X2(s)↓\ce{Ca^{2+}(aq) + 2OH^-(aq) -> Ca(OH)2(s) v}

Test for Cl⁻: AgNO₃ + NH₃

AgCl(s)+2 NHX3(aq)→[Ag(NHX3)X2]X+(aq)+ClX−(aq)\ce{AgCl(s) + 2NH3(aq) -> [Ag(NH3)2]+(aq) + Cl-(aq)}

Test for Br⁻: AgNO₃ + NH₃

AgBr(s)+2 NHX3(aq)→[Ag(NHX3)X2]X+(aq)+BrX−(aq)\ce{AgBr(s) + 2NH3(aq) -> [Ag(NH3)2]+(aq) + Br-(aq)}

Test for I⁻: AgNO₃

AgI(s)→AgI(s)\ce{AgI(s) -> AgI(s)}

Test for H₂ gas

HX2(g)+OX2(g)→HX2O(l)\ce{H2(g) + O2(g) -> H2O(l)}

Test for O₂ gas

2 C(s)+OX2(g)→2 CO(g)\ce{2C(s) + O2(g) -> 2CO(g)}

Test for CO₂ with limewater

COX2(g)+Ca(OH)X2(aq)→CaCOX3(s)v+HX2O(l)\ce{CO2(g) + Ca(OH)2(aq) -> CaCO3(s)v + H2O(l)}

Test for NH₃ gas

NHX3(g)+HCl(g)→NHX4Cl(s)\ce{NH3(g) + HCl(g) -> NH4Cl(s)}

Test for Cl₂ gas

ClX2(g)+HX2O(l)→HCl(aq)+HClO(aq)\ce{Cl2(g) + H2O(l) -> HCl(aq) + HClO(aq)}

Electrochemistry

Electrolysis of molten NaCl

Cathode: NaX++eX−→NaAnode: 2 ClX−→ClX2+2 eX−\text{Cathode: }\ce{Na+ + e^- -> Na}\\\text{Anode: }\ce{2Cl^- -> Cl2 + 2e^-}

Electrolysis of molten PbCl₂

Cathode: PbX2++2 eX−→PbAnode: 2 ClX−→ClX2+2 eX−\text{Cathode: }\ce{Pb^{2+} + 2e^- -> Pb}\\\text{Anode: }\ce{2Cl^- -> Cl2 + 2e^-}

Electrolysis of molten PbBr₂

Cathode: PbX2++2 eX−→PbAnode: 2 BrX−→BrX2+2 eX−\text{Cathode: }\ce{Pb^{2+} + 2e^- -> Pb}\\\text{Anode: }\ce{2Br^- -> Br2 + 2e^-}

Electrolysis of molten Al₂O₃

Cathode: AlX3++3 eX−→AlAnode: 2 OX2−→OX2+4 eX−\text{Cathode: }\ce{Al^{3+} + 3e^- -> Al}\\\text{Anode: }\ce{2O^{2-} -> O2 + 4e^-}

Electrolysis of concentrated NaCl(aq)

Cathode: 2 HX2O+2 eX−→HX2+2 OHX−Anode: 2 ClX−→ClX2+2 eX−\text{Cathode: }\ce{2H2O + 2e^- -> H2 + 2OH^-}\\\text{Anode: }\ce{2Cl^- -> Cl2 + 2e^-}

Electrolysis of dilute NaCl(aq)

Cathode: 2 HX2O+2 eX−→HX2+2 OHX−Anode: 4 OHX−→OX2+2 HX2O+4 eX−\text{Cathode: }\ce{2H2O + 2e^- -> H2 + 2OH^-}\\\text{Anode: }\ce{4OH^- -> O2 + 2H2O + 4e^-}

Electrolysis of CuSO₄(aq) (inert electrodes)

Cathode: CuX2++2 eX−→CuAnode: 4 OHX−→OX2+2 HX2O+4 eX−\text{Cathode: }\ce{Cu^{2+} + 2e^- -> Cu}\\\text{Anode: }\ce{4OH^- -> O2 + 2H2O + 4e^-}

Electrolysis of CuSO₄(aq) (Cu electrodes)

Cathode: CuX2++2 eX−→CuAnode: Cu→CuX2++2 eX−\text{Cathode: }\ce{Cu^{2+} + 2e^- -> Cu}\\\text{Anode: }\ce{Cu -> Cu^{2+} + 2e^-}

Electrolysis of acidified water (dilute H₂SO₄)

Cathode: 2 HX++2 eX−→HX2Anode: 2 HX2O→OX2+4 HX++4 eX−\text{Cathode: }\ce{2H^+ + 2e^- -> H2}\\\text{Anode: }\ce{2H2O -> O2 + 4H^+ + 4e^-}

Rates & Equilibrium

Reversible: Haber process

NX2(g)+3 HX2(g)⇌2 NHX3(g)\ce{N2(g) + 3H2(g) <=> 2NH3(g)}

Reversible: Contact process (SO₂ oxidation)

2 SOX2(g)+OX2(g)⇌2 SOX3(g)\ce{2SO2(g) + O2(g) <=> 2SO3(g)}

Reversible: Thermal dissociation of NH₄Cl

NHX4Cl(s)⇌NHX3(g)+HCl(g)\ce{NH4Cl(s) <=> NH3(g) + HCl(g)}

Reversible: CO₂ dissolution and carbonic acid formation

COX2(g)+HX2O(l)⇌HX2COX3(aq)\ce{CO2(g) + H2O(l) <=> H2CO3(aq)}

Reversible: Thermal dissociation of CaCO₃

CaCOX3(s)⇌CaO(s)+COX2(g)\ce{CaCO3(s) <=> CaO(s) + CO2(g)}