2.1.3

• amount of substance: the quantity of a substance that is present in a sample = number of particles present
• mole: the unit for the amount of substance compared to 12g of carbon 12
• Avogadro constant: the number of particles per mole, 6.02 x 10^23
• molar mass: the mass per mole, gmol^-1, equal to the Mr or RFM
• molar gas volume: gas volume per mole, dm^3 mol^-1, RTP unless stated otherwise
• empirical formula: simplest whole-number ratio of atoms of different elements in a compound
• Molecular formula: The actual number of atoms of each element in a molecule.
• How to calculate empirical formula: mass of element/ mass of compound in a ratio, divide all by the smallest number
• How to calculate molecular formula: empirical mass/ Mr
• anhydrous: without water
• hydrated: with water
• Water of crystallisation: The water that is present in the crystals And Chemically bonded
• moles = mass / mr
• moles = gas volume / rtp or molar gas volume
• moles = concentration x volume
• pressure (pa) x volume (m^3) = moles x 8.31 x temperature (K)
• percentage yield = actual moles of product / maximum theoretical moles of product x 100
• atom economy = number of moles of product / number of moles of reactants x 100
• benefits of a high atom economy: lower costs, more efficient use of resources, less waste, less pollution
• number of moles = number of particles / 6.02 x 10^23
• mass / molar mass = moles
• to find the amount of water in an anhydrous salt find the moles of the metal salt and water left and divide them
• to convert from g dm-3 to mol dm-3 divide by the RFM
• mass / volume = concentration g dm-3
• stoichiometry is the calculation of quantities of reactants or products needed based on moles of each
• mass is measured using a weighing scale
• gas volume is measured using a gas syringe or inverted measuring cylinder in water
• solution volume is measured using a measuring cylinder
• actual moles x (percentage yield / 100) = expected moles