Moles & Calculations (IGCSE)
Year 11 (IGCSE) ⚛️ Particles & Structure Apply mole calculations to titrations, gas volumes and percentage yield.
🧮 Mole Calculations
At IGCSE, mole calculations extend to concentrations, gas volumes, percentage yield and atom economy.
Key Formulas
$$n = \frac{m}{M_r} \quad n = C \times V \quad n = \frac{V}{24} \text{ (RTP)} \quad n = \frac{V}{22.4} \text{ (STP)}$$ V must be in dm³. 1000 cm³ = 1 dm³. RTP = room temperature and pressure.
📊 Concentration
Concentration
$$C = \frac{n}{V} \quad (mol/dm^3) \qquad n = C \times V \qquad V = \frac{n}{C}$$Example: 5.85 g NaCl (Mr=58.5) in 500 cm³:
n = 5.85/58.5 = 0.1 mol. V = 0.5 dm³. C = 0.1/0.5 = 0.2 mol/dm³
n = 5.85/58.5 = 0.1 mol. V = 0.5 dm³. C = 0.1/0.5 = 0.2 mol/dm³
📈 Yield & Atom Economy
%yield: If theoretical = 34 g and actual = 5 g: yield = 5/34 × 100 = 14.7%
Atom economy: 2NH₄Cl → N₂ + 2HCl + 2H₂O
Desired product N₂ (Mr=28); all products (2×54 + 28 + 36) = ...
High atom economy = less waste = green chemistry.
Atom economy: 2NH₄Cl → N₂ + 2HCl + 2H₂O
Desired product N₂ (Mr=28); all products (2×54 + 28 + 36) = ...
High atom economy = less waste = green chemistry.
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🧮 Full Mole & Yield Calculator
Gas Volume at RTP (24 dm³/mol) or STP (22.4 dm³/mol)
Percentage Yield