The Mole and Chemical Calculations
Think of the mole as chemistry's way of counting massive numbers of tiny particles - it's like saying "a dozen" but for atoms and molecules. One mole always contains 6.02 × 10²³ particles, which is called Avogadro's number.
You'll use three main formulas constantly: mol = mass ÷ Mr (for solid calculations), mol = concentration × volume (for solutions), and the ideal gas equation PV = nRT (for gases). The key is identifying which type of substance you're dealing with first.
Top Tip: Always check your units! Convert cm³ to dm³ by dividing by 1000, and remember that pressure must be in pascals (Pa) for the ideal gas equation.
For gas calculations, the ideal gas equation connects pressure, volume, temperature and moles. Just remember that temperature must be in Kelvin (add 273 to Celsius) and volume in m³ (multiply cm³ by 10⁶).
