16 April 2020
Soluble or insoluble?
What do these terms mean?
Water Treatment
Fertilisers

16 April 2020
7.3 Making salts from solutions
• Indicators are needed to check producing a soluble salt from an alkali and acid.
• Insoluble salts produce a precipitate when reacting two solutions.
• Precipitation is an important way of removing some substances from waste water.
Soluble = Able to dissolve in a solvent.
Insoluble = Unable to dissolve in a solvent.
Precipitate = A solid material produced from a solution.

Acid + alkali
A neutralisation reaction is where an acid reacts with a alkali to produce a neutral solution of a salt and water. alkali sodium hydroxide pH 14 hydrochloric acid pH 1 neutralisation
Salt sodium chloride pH 7
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Increasingly acid Increasingly alkali
How can the salt be separated from the water?

Neutralisation reactions: hydroxides
Each OH ion reacts with one H + ion.
Reaction with hydroxides: H + + OH  H
2
O
Eg. Potassium +hydrochloric  water + potassium hydroxide acid chloride
K OH + H Cl  H
2
O + KCl
Eg. Calcium + sulphuric  water + calcium hydroxide acid sulphate
Ca( OH )
2
+ H
2
SO4  2H
2
O + CaSO
4
Water can be evaporated to leave the salt behind.

• A precipitation reaction leaves behind a solid material. E.g.
Lead Nitrate + Sodium Chloride → Lead Chloride + Sodium Nitrate
Pb(NO
3
)
2 (aq)
+ 2NaCl
(aq)
→ PbCl
2 (s)
+ 2NaNO
3 (aq)
Practical
1. Add sodium chloride to lead nitrate and stir.
2.Filter the precipitate.
3.Wash and dry precipitate. Place on a watch glass.
4.Write down what the Lead Chloride looks like.

16 April 2020
7.3 Making salts from solutions
• Indicators are needed to check producing a soluble salt from an alkali and acid.
• Insoluble salts produce a precipitate when reacting two solutions.
• Precipitation is an important way of removing some substances from waste water.
Soluble = Able to dissolve in a solvent.
Insoluble = Unable to dissolve in a solvent.
Precipitate = A solid material produced from a solution.