Chemistry GCSE making salts methods, solubility rules, and indicator colours

Make a soluble salt from an insoluble reactant

1. Heat the acid to speed up the rate of reaction

2. Add the base until it is in excess (when no more dissolves) and stir with a glass rod to neutralise all the acid

3. Filter the mixture using filter paper and a funnel to remove any excess solid

4. Heat the filtered solution to evaporate some of the water until crystals form on the end of the glass rod Filter

5. Allow the solution to cool so the crystals form

6. Remove the crystals by filtration and dry them in a dessicator to evaporate any remaining water

7. Use copper oxide and sulfuric acid to form copper sulfate and water

8. Sometimes called the excess base method

Make an insoluble salt from two soluble reactants

1. Add water to each salt to dissolve the salts and make them aqueous

2. Mix the two salt solutions together in a beaker and stir with a glass rod to ensure all the reactants have reacted

3. Filter using filter paper and a funnel to remove the precipitate that has formed (this is the insoluble salt)

4. Wash with distilled water to remove the other soluble salt that has formed and any other impurities

5. Leave it in a dessicator so the water evaporates

6. Use lead nitrate and magnesium sulfate to form lead sulfate (the insoluble salt) and magnesium nitrate (the soluble salt)

7. Sometimes called the precipitation method

Solubility rules

1. All nitrates are soluble

2. Common sodium, potassium, and ammonium salts are soluble

3. Common chlorides are soluble except silver and lead

4. Common sulfates are soluble except barium, calcium, and lead

5. Common carbonates are insoluble except sodium, potassium, and ammonium

6. Common hydroxides are insoluble except sodium, potassium, and calcium

Colours of indicators

Universal Indicator - red in strong acids, orange / yellow in weak acids, green in neutral, light blue in weak alkalis, purple in strong alkalis

Litmus paper - red in acids, blue in alkalis

Phenolphthalein - colourless in acids, pink in alkalis

Methyl orange - red in acids, yellow in alkalis, orange in neutral