2.1.3 amount of substance

Amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon-12

Average mass of one atom compared to 1/12th of the mass of one atom of carbon-12

Mass in grams of 1 mole of a substance g mol-1

Adding up the mass numbers (from the periodic table) of each element in the compound

Volume of 1 mole of a gas at a given temperature and pressure. All gases have this same volume At room pressure (1atm) and room temperature (25C) the molar gas volume is 24dm3 mol-1

6.02x10^23 atoms in 12 grams of carbon-12

Moles = grams/ RAM

Simplest whole number ratio of atoms of each element in the compound

• Divide each mass by the atomic mass of the element • Divide each number by the smallest one • Sometimes you may need to multiply to get whole numbers

Actual number of atoms of each element in the compound

Contains water of crystallisation

Heating in a crucible • Weigh an empty dry crucible and lid • Add 2g of hydrated CaSO4 to the crucible and weigh again • Heat strongly with a Bunsen for a couple of minutes • Allow to cool • Weigh crucible and contents again • Heat crucible again and reweigh until you reach a constant mass

Concentration = moles / volume dm3

Mass concentration = mass / volume g dm3

Weigh sample bottle containing required mass of solid on 2dp balance Transfer to beaker and re weigh bottle Record difference in mass Add 100cm3 distilled water to beaker. Use glass rod to stir to help dissolve the solid Pour solution into 250cm3 graduated flask via a funnel Rinse beaker and funnel and add washings from beaker and glass rod to volumetric flask Make up to the mark with distilled water using a dropping pipette Invert flask several times to ensure uniform solution

Pipette 25cm3 of original solution into 250cm3 volumetric flask Make up to the mark with distilled water using a pipette for last few drops Invert flask several times to ensure uniform solution

New diluted concentration = original concentration x (original volume / new diluted volume)

Irritant - dilute acid and alkalis- wear googles Corrosive- stronger acids and alkalis wear goggles Flammable – keep away from naked flames Toxic – wear gloves- avoid skin contact- wash hands after use Oxidising- Keep away from flammable / easily oxidised materials

Gas volume dm3 = amount x 24

Amount of substance (in mol) x avogadros constant

Density = mass / volume G cm-3

Percentage yield = (actual yield/theoretical yield) x 100 • Work out moles of reactant • Use balanced equation to give moles of product • Work out mass of product • Use equation

Atom economy = (mass of useful products/ mass of all reactants) x 100 So, (moles x Mr of product) / (moles x mr of reactant (do all)) x100