Making Insoluble Salts

Question 1

which salts are always soluble?

Answer 1

common salts of:
- sodium (Na+)
- potassium (K+)
- ammonium (NH4+)
and nitrates (NO3-)

Question 2

are common chlorides (Cl-) soluble?

Answer 2

yes, except with silver chloride and lead chloride

Question 3

are common sulfates (SO42-) soluble?

Answer 3

yes, except with lead, barium and calcium sulfate

Question 4

are common carbonates (CO32-) soluble?

Answer 4

no, except for sodium, potassium and ammonium ones

Question 5

are common hydroxides (OH-) soluble?

Answer 5

no, except for sodium, potassium and calcium ones (calcium hydroxide is slightly soluble)

Question 6

are common oxides (O2-) soluble?

Answer 6

no, except with sodium, potassium and ammonium ones

Question 7

how do you make an insoluble salt?

Answer 7

by using a precipitation reaction - pick the right two soluble salts and react them together to get your insoluble salt

Question 8

what is the word and symbol formula for making the insoluble salt lead sulfate?

Answer 8

lead nitrate + magnesium sulphate -> lead sulphate + magnesium nitrate

Pb(NO3)2 (aq) + MgSO4 (aq) -> PbSO4 (s) + Mg(NO3)2 (aq)

Question 9

lead sulphate practical

Answer 9

1. add one spatula of lead nitrate to a test tube and add water to dissolve it - you should use deionised water to make sure there are no other ions about
2. shake thoroughly to ensure that all the lead nitrate has dissolved and then in a separate test tube, do the same with one spatula of magnesium sulphate
3. tip the two solutions in a small beaker and give it a good stir to make sure its all mixed together - the lead sulphate should precipitate out
4. put a folded piece of filter paper into a filter funnel and stick the funnel into a conical flask
5. pour the contents of the beaker into the middle of the filter paper and make sure that the solution doesn’t go above the filter paper, otherwise some of the solid could dribble down the side
6. swill out the beaker with more deionised water, and tip this into the filter paper to make sure you get all the precipitate from the beaker
7. rinse the contents of the filter paper with deionised water to make sure that all the soluble magnesium nitrate has been washed away
8. scrape the lead sulphate onto fresh filter paper and leave it to dry in an oven or desiccator