This key facts covers Key Facts to Memorise within Moles & Calculations for GCSE Chemistry. Revise Moles & Calculations in Quantitative Chemistry for GCSE Chemistry with 22 exam-style questions and 20 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 7 of 15 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 7 of 15
Practice
22 questions
Recall
20 flashcards
📌 Key Facts to Memorise
- Avogadro's constant = 6.02 × 10²³ particles per mole — this is the number of atoms in exactly 12g of carbon-12
- The golden equation: n = m ÷ Mr (moles = mass ÷ relative formula mass)
- Conservation of mass: atoms are rearranged, never created or destroyed — total mass in = total mass out
- Coefficients in equations give you the mole ratio (e.g., 2Mg + O₂ → 2MgO means 2 moles Mg : 1 mole O₂ : 2 moles MgO)
- Unit conversions: 1 dm³ = 1000 cm³ = 1 litre (CRUCIAL for concentration calculations!)
- Concentration: c = n ÷ V (mol/dm³) or c = m ÷ V (g/dm³)
- Percentage yield = (actual yield ÷ theoretical yield) × 100 — always less than 100% in practice
- Atom economy = (Mr of desired product ÷ total Mr of all products) × 100 — higher is greener!