Chemical Energetics
Chemical Energetics — Formulae Sheet (Tabular Form)
| Concept | Formula | Units | Key Notes |
|---|---|---|---|
| Enthalpy Change | ΔH = H(products) − H(reactants) | kJ mol⁻¹ | Negative = exothermic, Positive = endothermic |
| Heat Energy | q = mcΔT | J | m = mass (g), c = specific heat capacity |
| Temperature Change | ΔT = final − initial | °C or K | Same value in °C and K |
| Specific Heat Capacity | c = q / (mΔT) | J g⁻¹ °C⁻¹ | Rearranged formula |
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change O Level And IGCSE Chemistry Full Scale Course
| Concept | Formula | Units | Key Notes |
|---|---|---|---|
| Enthalpy Change from Heat | ΔH = − q / n | kJ mol⁻¹ | Negative sign for exothermic |
| Bond Energy Calculation | ΔH = Σ(bonds broken) − Σ(bonds formed) | kJ mol⁻¹ | Breaking = endo, forming = exo |
| Average Bond Energy | Given in data tables | kJ mol⁻¹ | Used in calculations |
| Energy Change per Mole | ΔH = q / n | kJ mol⁻¹ | Adjust sign based on reaction |
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change O Level And IGCSE Chemistry Full Scale Course
| Concept | Formula | Units | Key Notes |
|---|---|---|---|
| Hess’s Law | ΔH = ΣΔH(products) − ΣΔH(reactants) | kJ mol⁻¹ | Path independent |
| Combustion Enthalpy | ΔHc = heat released per mole burned | kJ mol⁻¹ | Always exothermic |
| Neutralisation Enthalpy | ΔHn = heat released per mole water formed | kJ mol⁻¹ | Acid + base reaction |
| Formation Enthalpy | ΔHf = formation of 1 mol compound | kJ mol⁻¹ | From elements |
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change O Level And IGCSE Chemistry Full Scale Course
| Concept | Formula | Units | Key Notes |
|---|---|---|---|
| Energy Efficiency | % efficiency = (useful energy / total energy) × 100 | % | Industrial processes |
| Calorimetry (Solution) | q = mcΔT | J | Often water used (c = 4.18) |
| Heat per Mole | ΔH = q / n | kJ mol⁻¹ | Convert J → kJ if needed |
| Fuel Energy | Energy released per mole or per gram | kJ mol⁻¹ | Compare fuels |
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change O Level And IGCSE Chemistry Full Scale Course
| Concept | Formula | Units | Key Notes |
|---|---|---|---|
| Exothermic Reaction | ΔH < 0 | — | Temperature increases |
| Endothermic Reaction | ΔH > 0 | — | Temperature decreases |
| Energy Profile | Activation energy = peak − reactants | kJ mol⁻¹ | Shows pathway |
| Activation Energy | Eₐ = energy needed to start reaction | kJ mol⁻¹ | Not always calculated |
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change O Level And IGCSE Chemistry Full Scale Course