The pH scale

Alkaline

Acid

Neutral

•Hydrogen Ions make acidic solutions

•Hydroxide ions make basic/alkaline solutions.

•Bases are substances that can neutralise acids. They are usually metal oxides or metal hydroxides.

•Alkalis are soluble bases

Neutralisation

• The acid reacts with the alkali to form a salt and water which is a neutral solution. The hydrogen ions in the acid join with the hydroxide ions in the alkali to form a neutral water molecule. The gas in the acid reacts with the metal or ammonium in the alkali to form an ionic salt.

• E.g.

Hydrochloric acid + sodium hydroxide -> sodium chloride +water

HCl(aq) + NaOH(aq) -> NaCl(aq) + H20 (l)

H+ (aq) + OH-

(aq) -> H2O (l)

Reactions of Salts

Acid + Metal -> a salt + hydrogen

E.g. Sulphuric acid + potassium -> potassium sulphate + hydrogen

This is a displacement reaction

Acid + Base -> a salt + water

E.g. Sulphuric acid + sodium oxide -> sodium sulphate + water

This is a Neutralisation reaction

Acid + Alkali -> a salt + water

E.g. Sulphuric acid + potassium hydroxide -> potassium sulphate + water

This is a neutralisation reaction

Acid + Carbonate -> a salt + water + carbon dioxide

E.g. Sulphuric acid + copper carbonate -> copper sulphate + water + carbon dioxide

Naming Salts

Sodium Chloride

type of metal or ammonium in the

base/alkali/metal/carbonate which reacts with the acid

This comes from the acid

Remember

•Hydrochloric acid makes chloride salts

•Sulphuric acid makes sulphates

•Nitric acid makes nitrates

Precipitation Reactions

• This is a reaction where a solid insoluble salt is produced when two soluble salt solutions are mixed together. This type of reaction is important when we want to remove heavy metal ions from polluted water.

• E.g. Lead nitrate + Sodium chloride -> lead chloride + sodium nitrate

Pb(NO3)2(aq) + 2NaCl(aq) -> PbCl2(s) + 2NaNO3(aq)

• E.g.

Silver nitrate + potassium iodide -> silver iodide + potassium nitrate

AgNO3(aq) + KI2(aq) -> AgI(s) + KNO3(aq)

Questions1. Name the salt which is produced when hydrochloric acid reacts

with ammonium hydroxide.

2. Which ions make acidic solutions?

3. What is an alkali?

4. Write the balanced symbol equation for sulphuric acid + potassium. Include the state symbols

5. What is produced in a precipitation reaction?

6. What is the equation for a neutralisation reaction?

Answers

1. Ammonium Chloride

2. Hydrogen Ions

3. A soluble base

4. H2SO4(aq) + K(s) -> KSO4(aq) + H2(g)_

5. An insoluble salt

6. H+ (aq) + OH-(aq) -> H2O (l)