2g Acids, bases and salt preparations

Question 1

How do you make soluble salts?

Answer 1

using a neutralisation reaction

Stage 1 – THE REACTION
react the acid with an insoluble substance (e.g. a metal, metal oxide,
metal carbonate or metal hydroxide) to produce the desired salt

the mixture may need to be heated

add the insoluble substance until it no longer reacts

Stage 2 – FILTER OFF THE EXCESS
filter off the left over insoluble metal / base

Stage 3 – CRYSTALISE THE SALT
heat the solution to evaporate some water until crystals start to form

leave the solution to cool down – more crystals will form as it cools

filter off and wash the crystals of the salt

allow the crystals to dry

Question 2

How do you make sure that all acid is reacted in step 1?

Answer 2

• Add it until no more will physically dissolve
• stir it thoroughly

Question 3

What is the purpose of step 2?

Answer 3

So that the unreacted or excess solution gets separated from the soluble salt

Question 4

How could a pure sample of an insoluble salt be separated from the remaining solutions?

Answer 4

filtration

Question 5

How do you make an insoluble salt?

Answer 5

using a precipitation reaction
This involves mixing two soluble salts in a solution, which reacts to form an insoluble salt that precipitates, or falls out of the solution.

e.g. - Using a dropper, add sodium sulfate to a depth of about 2cm
- Using a second dropper, add a 2cm depth of lead(II) nitrate to the same test tube
- Filter the solution into a beaker. Rinse the residue with distilled water
- Carefully remove the filter paper and residue from the funnel and lay it on a watch glass
- Allow salt to dry
Sodium sulfate + lead(II) nitrate -> sodium nitrate + lead(II) sulfate