Atoms, Elements And Compounds
Atoms, Elements And Compounds — Formulae Sheet (Tabular Form)
| Concept | Formula | Units | Key Notes |
|---|---|---|---|
| Relative Atomic Mass | Aᵣ = (Σ (isotopic mass × abundance)) / 100 | — | Weighted average of isotopes |
| Relative Molecular Mass | Mᵣ = Σ Aᵣ | — | Sum of all atomic masses |
| Number of Moles | n = m / M | mol | m = mass, M = molar mass |
| Number of Particles | N = n × Nₐ | particles | Nₐ = 6.02 × 10²³ |
| Avogadro Constant | Nₐ = 6.02 × 10²³ | mol⁻¹ | Particles per mole |
| Empirical Formula | Simplest whole number ratio | — | Derived from mole ratio |
| Molecular Formula | Molecular = n × empirical | — | n = Mᵣ / empirical formula mass |
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 |
|---|---|---|---|
| Percentage Composition | % = (mass of element / total mass) × 100 | % | Used in empirical formula |
| Mass from Moles | m = n × M | g | Rearranged mole formula |
| Moles from Particles | n = N / Nₐ | mol | Converts particles to moles |
| Volume of Gas (RTP) | V = n × 24 | dm³ | For gases at RTP |
| Concentration | C = n / V | mol dm⁻³ | For solutions |
| Moles in Solution | n = C × V | mol | V in dm³ |
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 |
|---|---|---|---|
| Percentage Yield | % yield = (actual yield / theoretical yield) × 100 | % | Reaction efficiency |
| Percentage Purity | % purity = (pure mass / total mass) × 100 | % | Impurity calculation |
| Atom Economy | Atom economy = (Mr of desired product / total Mr of products) × 100 | % | Efficiency of reaction |
| Limiting Reagent | Based on smallest mole ratio | — | Determines yield |
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 |
|---|---|---|---|
| Mass Ratio | From balanced equation | — | Compare moles then masses |
| Mole Ratio | From coefficients in equation | — | Used in calculations |
| Volume Ratio (Gases) | Volume ∝ moles | — | Same T and P |
| Ionic Charge Balance | Total positive = total negative | — | Compound neutrality |
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 |
|---|---|---|---|
| Density (Reused) | ρ = m / V | kg m⁻³ | Sometimes used in compound calc |
| Empirical from % | Convert % → moles → ratio | — | Step method |
| Molecular Formula Step | n = Mᵣ / empirical mass | — | Multiply empirical |
| Conservation of Mass | Total mass reactants = products | — | Always applies |
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