Section 1 e) Specification

1.21 write word equations and balanced chemical equations to represent the
reactions studied in this specification

Copper + Oxygen --> Copper Oxide
2Cu + O2 --> 2CuO

Carbon + Oxygen --> Carbon Dioxide
C + O2 --> CO2

Hydrogen + Oxygen --> Water (Dihydrogen Monoxide)
2H2 + O2 --> 2H2O

1.22 use the state symbols (s), (l), (g) and (aq) in chemical equations to
represent solids, liquids, gases and aqueous solutions respectively

(s) - the substance is solid at room temp (unless otherwise specified in the question)
(l) - the substance is liquid at room temp (unless otherwise specified in the question)
(g) - the substance is gas at room temp (unless otherwise specified in the question)
(aq) - the substance is dissolved in water

1.23 understand how the formulae of simple compounds can be obtained
experimentally, including metal oxides, water and salts containing water of
crystallisation

Through experiments to remove an element from a compound, the chemical formula can be derived. The reactants are first weighed, and then the mixture is split (You could work out a metal oxide or salt)

Metal Oxide
Weigh a crucible with its lid, then place magnesium inside and weigh again, recording the measurements.
Heat it strongly over a roaring bunsen flame, and gently open the lid with tongs momentarily, to allow oxygen to get in without letting the magnesium oxide escape.
Weigh it every so often so you can see how the mass is changing. When the mass stops changing, the reaction is complete.
Record the final mass of the magnesium oxide and crucible, and use the numbers you recorded earlier to determine the mass of magnesium and the mass of oxygen.
Using each element's relative atomic mass, the empirical formula can be determined.

Salt (crystallisation)
Weigh an evaporating basin, then add hydrated copper sulfate and weigh again.
Heat the solution over a bunsen burner, gently stirring to ensure even heating.
Stir until the solution loses colour, indicating all water has been lost.
Weigh again to find the mass of water lost, and also the mass of anhydrous copper sulfate.
Divide mass by Mr of the copper sulfate, and do the same with water.
Simplify this to find the ratio of water to copper sulfate, and round to the nearest whole number,
e.g. CuSO4 ● 5H2O

1.24 calculate empirical and molecular formulae from experimental data

By weighing compounds, then extracting an element from them through a chemical reaction and recording the change in mass, then making these masses into percentages and dividing by Ar, we can find the number of atoms of it in a molecule. Empirical and molecular formulae of compounds and elements can be found this way.

1.25 calculate reacting masses using experimental data and chemical equations

The mass of the reactants is always equal to the mass of the products. Using this principle, applied to equations, we can calculate the different masses.

1.26 calculate percentage yield

(yield retrieved  x 100 )/ full potential yield = percentage yield

The expected or potential yield can be calculated in a reacting mass calculation, however we are not always able to recover the full yield. The amount we retrieve can be calculated as a percentage of the full potential yield using the above equation.

1.27 carry out mole calculations using volumes and molar concentrations.

Using the above formula triangle, the moles, volume and concentration (molar volume) can be calculated in a chemical equation.