Making Salts

Question 1

What’s soluble?

Answer 1

• all NITRATES
• all SODIUM, POTASSIUM, and AMMONIUM compounds
• most common CHLORIDES (ex. silver, lead)
• most SULFATES (ex. barium, calcium, lead)

Question 2

What’s insoluble?

Answer 2

• most CARBONATES (ex. sodium, potassium, ammonium)
• most METAL HYDROXIDES, METAL OXIDES
• lead chloride, silver chloride
• barium sulfate, calcium sulfate, lead sulfate

Question 3

Making soluble salts using acids and insoluble bases

Answer 3

acid + insoluble base

1) add the insoluble base (e.g. most carbonates, metal hydroxides and metal oxides) to the acid
2) The insoluble base will dissolve
3) You know the reaction is completed, and the acid is neutralised, when the excess solid sinks to the bottom and stays there
4) Filter the excess base to get a salt solution
5) Evaporate for pure salt crystals

Question 4

Making soluble salts using an alkali

Answer 4

Alkalis are SOLUBLE bases so you can’t use the other method because…

• you can’t filter them out if you add too much
• can’t tell when you’ve added too much
  1) Titration. Use an indicator to tell exactly how much acid is needed to neutralise the acid, and then repeat without an indicator so uncontaminated

Question 5

Making insoluble salts - precipitation reactions

Answer 5

Just the mixing of two solutions which contain the ions you need.

eg. 1) to make barium sulphate (insoluble) you need a solution containing barium ions, and a solution containing sulphate ions.
2) So, mix barium chloride (most chlorides are soluble) with sulphuric acid.

Question 6

Titrations

Answer 6

Help find out exactly how much acid is needed to neutralise a base (or vise vera)

1) Using a pipette and pipette filler, add alkali and indicator to a conical flask
2) Fill a burette with acid
3) Add the acid bit by bit until you see a colour change
4) Record amount used and repeat without indicator