Preparation of salts

There are 3 ways to prepare salt in the lab, and I will show you how to remember which are the techniques to use for the different salts.

1. Precipitation - this is only for preparation of insoluble salts e.g. lead (II) chloride, barium sulfate & lead (II) carbonate.

2. Titration - this is for the preparation of soluble salts, such as sodium, potassium & ammonium.

3. Acid + excess insoluble substance - usually for other soluble salts, less the ones listed in method 2.

I will go into details how this is done during my tuition classes.

Oxidation-reduction reactions

Neutralisation reaction

Why is copper (II) sulfate sometimes 'blue' and other times 'white' in colour?

The copper (II) sulfate crystals that you see in the lab are obviously blue in colour. The same goes for the copper (II) sulfate solution. This is because copper (II) sulfate is hydrated, meaning to say it has water of crystallisation attached to the salt.

CuSO4.5H2O -----------------------> CuSO4 + 5H2O



Once you heat the copper (II) sulfate crystals, they will lose the water of crystallisation, thus forming white powder. Copper (II) sulfate is said to be 'anhydrous', meaning 'dry'.

Anhydrous copper (II) sulfate powder is also used to test for the presence of water.

Addition reactions of alkenes

Writing ionic equations

Many of my students have problems writing ionic equations. If you understand how this works, then this will not be a problem at all. The most important thing that you need to bear in mind is to find out if that particular substance is soluble in water in the first place.

Follow the following steps.

1. Write down a balanced chemical equation, including the state symbols.

2. For those substances that are soluble in water i.e. aqueous (aq), break them up into the ions.

3. Cancel the spectator ions i.e. those that appear before and after the reaction.

4. Finalise the ionic equation. Make sure that this is balanced as well, including the charges.

Final notes:

1. There are some equations that do not have any ionic equations, simply because there are no ions involved.

2. An ionic equation shows the actual reaction that is going on.

Substitution reaction of methane

Common unit cnoversions

Density-related problems

How surface area affects speed of reaction

How temperature affects the rate of reaction

Extraction of iron in the blast furnace

Reaction of lithium with water