Acids, Alkalis & pH Scale Flashcards
Indicators
Indicators are chemicals that change colour in the presence of an acid or alkali
Universal indicator
A mixture indicators. It is useful because it shows a range of colours from pH 1-14
Acids are substances that:
- Have a pH below 7 and turn universal indicator yellow, orange or red
- Turns Linus paper red
- Form solutions containing hydrogen ions (H+)
- Hydrochloric acid is a strong acid
- Ethononic acid is a weak acid
Alkalis are substances that:
- Have a pH above 7 and turn universal indicator blue or purple
- Turns Linus paper blue
- Can neutralise acids
- Form solutions containing hydroxide ions(OH-)
- Sodium hydroxide is a strong alkali
- Ammonia is a weak alkali
Neutralisation Formula
H+ + OH- = H2O
From From Water
Acid Alkali
Aqueous solution
A substance that has been dissolved in water
Acid
A substance that has been dissolves in water to produce hydrogen ions (H+) and has a pH of less than 7
Alkali
A base that dissolves in water to produce hydroxide ions (OH-)
Base
A substance that has a pH greater than 7
pH scale
A measure of how acidic or alkaline a solution is
Neutralisation
The reaction between an acid and base to make salt and water
Strong acid/alkali
An acid/alkali that ionises completely in water
Weak acid/alkali
An acid/alkali that does not ionise completely in water
Soluble
Dissolve in the solvent
Key information
- Acid + Metal = salt + hydrogen
- Acid + Metal Carbonate = Salt + Water + Carbon Dioxide
- Acid + Alkali( metal oxide or metal hydroxide) = Salt + Water
