Acids and alkalis

Acids:

• pH < 7
• Turns litmus paper/ universal indicator red
• Forms solutions containing H  ions

Alkalis:

• pH > 7
• Turns litmus paper/ universal indicator blue
• Forms solutions containing OH  ions

Bases:

• All alkalis are bases, but not all bases are alkalis
• Alkalis are soluble bases
• Substances that react with acids by absorbing H  ions
• Oxides, hydroxides, carbonated etc

Acid + Base/ Alkali = Salt + Water

Acid + Metal oxide = Salt + Water

Acid + Metal = Salt + Hydrogen

Salt + Salt = Diff. Salt and Diff. Salt (see precipitation)

Acid + Carbonate = Salt + Water + Carbon Dioxide

Acid + Alkali:

• Water is formed because the H  ions react with the OH  ions to form H O

• Any reaction that produced an insoluble compound when two aqueous solutions are mixed
• It is impossible to predict unless we know the physical state of all the reactants and products

aq + aq = s + aq

To work out whether a precipate is formed:

• Write down the names of the reactants
• Write down the ions in the reactants
• Swap the ions
• If one of the resulting salts are insoluble a precipitate has been formed