1.7 Quantitative Chemistry

The mass of the atom compared with that of the carbon 12 isotope, which has a mass of exactly 12 and it is the weighted mean mass of the mass numbers

The sun of the relative atomic mass of all the atoms present in the formula of a substance

Add all masses together, multiplying by the power when needed

RAM of element / Mr of whole compound x 100

A measurement of chemical amounts. The mass of one mole of a substance in grams is numerically equal to the Mr Eg magnesium: mass (24g) / Mr (24) = 1 mole

Mr (masses added together)

n = m / Mr m = n x Mr

The one that runs out first

Actual yield / theoretical yield x 100

Divide known mass by the Mr of its compound/element to get its moles, apply ratio, multiply by the unknown compound/element’s Mr

Incomplete reaction Impossible to separate product fully out of the reaction mixture Reaction is reversible and may not go to completion As a result of a side reaction

The simplest whole number ratio of the atoms of each element in a compound

Actual number of atoms of each element in a molecule

Solid crystals contain water of crystallisation

Does not contain water of crystallisation

Water that is chemically bonded into the crystal structure of a compound

Heating to constant mass

Reheating and reweighing until a constant mass is observed. This ensures that all the water of crystallisation has been removed from the hydrated crystals

Total Mr of water / total Mr of compound x 100

Eg finding the x. Make a table for the compound and its woc. Figure out mass, Mr, therefore moles (divide) and the ratio will equal x (when simplified to 1:__)

Heating to constant mass