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7.3 Making salts from solutions
Soluble or insoluble? What do these terms mean?
April 19, 2023
Fertilisers
Water Treatment
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.
April 19, 2023
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 acidacid reacts with a alkalialkali to produce a neutral solution of a a saltsalt and waterwater.
1 2 14131211109876543
Increasingly acid Increasingly alkali
sodium hydroxidepH 14
hydrochloric acidpH 1
neutralisation
sodium chloridepH 7
Salt
alkalalkalii
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- H2O
Eg. Potassium +hydrochloric water + potassium hydroxide acidchloride
KOHOH + H HCl HH22OO + KClEg. Calcium + sulphuric water + calcium hydroxide acid sulphate
Ca(OHOH)22 + HH22SO4 2H2H22OO + CaSO4
Water can be evaporated to leave the salt behind.
Insoluble Salts
• A precipitation reaction leaves behind a solid material. E.g.Lead Nitrate + Sodium Chloride → Lead Chloride + Sodium
NitratePb(NO3)2 (aq) + 2NaCl (aq) → PbCl2 (s) + 2NaNO3 (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.
Filtering
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.
April 19, 2023
Soluble = Able to dissolve in a solvent.
Insoluble = Unable to dissolve in a solvent.
Precipitate = A solid material produced from a solution.