MAKING SALTS
METAL + ACID ----> SALT + HYDROGEN
Obtaining copper salt crystals
When metals react with acids they lose electrons to become positive ions
ACID + BASE ----> SALT + WATER
Alkalies are bases which are soluble in water
Most bases are metal oxides
Alkali metals never added to acid - too violent of a reaction
NEUTRALISATION REACTION
Obtaining sulfate crystals from copper oxide and sulfuric acid
- Add insoluble copper oxide to sulfuric acid and stir
- Warm gently over bunsen burner
- The solution will turn blue when the reaction is taking place (this is the copper sulfate). Excess black copper oxide can be seen
- Once reaction is complete, filter excess copper oxide
- Evaporate water until the first crystals start to appear around edge. Leave rest of water to evaporate slowly (larger crystals)
- Dry crystals to remove any excess solution
Salts are made up from + and - ions:
- positive ions = metals, base, carbonate
- negative ions = acid
- Measure acid, warm gently over bunsen burner - DON'T BOIL
- Add metal oxide to beaker whilst acid is warm and continue adding until no more dissolves
- Cool then filter out undissolved metal oxide
- Evaporate until volume halves (POINT OF CRYSTALLISATION), leave to crystallise at room temp
- Dry crystals with paper towel
ACID + ALKALI ---> SALT + WATER
NEUTRALISATION REACTION
Use an acid-base indicator to tell when reaction is complete, as no gas is given off and there is no excess insoluble solid
Obtaining crystals
- Use titration to find out how much acid is needed to neutralise the alkali
- Add this volume of acid to the alkali (NO INDICATOR)
- Heat and evaporate to form crystals
ACID + CARBONATE -----> SALT + WATER + CARBON DIOXIDE
Obtaining the crystals
- Add enough carbonate to the acid until no more dissolves
- Filter the unreacted metal carbonate
- Evaporate until solution is halved
- Leave to cool and crystallise