Chemistry salt preparation

Question 1

Salt reactions

Answer 1

1) Acid + metal carbonate ➡️ salt + water + carbon dioxide
2) acid + metal hydrogen carbonate ➡️ salt + water + carbon dioxide
3) acid + metal hydroxide ➡️ salt + water
4) acid + metal oxide ➡️ salt + water
5) acid + metal ➡️ salt + hydrogen

Question 2

Salt preparation 1

Answer 2

Soluble acid + soluble base ➡️ soluble salt + water

Purification - evaporation
Since a salt solution is produced, the solid salt needs to be isolated.
This is done by evaporation, to remove MOST of the water.
The crystalline salt can be dried on paper or left in a warm place/oven.

Question 3

Salt preparation 2

Answer 3

Soluble acid + insoluble base ➡️ soluble salt + water (+ CO2)
Procedure - neutralisation
Add excess insoluble base/carbonate so that all acid fully reacts
Forms a salt solution (dissolved in water)

Question 4

Salt preparation 2 - part 2

Answer 4

Purification- filtration THEN evaporation
Filtering the final solution removes any unreacted solid base.
Evaporating removes MOST of the water, as in the first method.

Question 5

Salt preparation 3

Answer 5

Soluble acid + soluble base ➡️ insoluble salt + soluble salt
Procedure - precipitation
When two soluble ionic salts are combined, they can form an insoluble salt; a precipitate

Question 6

Salt preparation 3 - part 2

Answer 6

Soluble acid + soluble base ➡️ insoluble salt + soluble salt
Purification - filtration
Filtering the mixture separates the insoluble salt, as the precipitate.

Question 7

Salt preparation 3 - part 3

Answer 7

Soluble acid + soluble base ➡️ insoluble salt + soluble salt
Purification- washing THEN drying
Washing the precipitate to remove soluble impurities.
Oven drying to obtain dry salt.

Question 8

Salt preparation 3 - part 4 example

Answer 8

Soluble acid + soluble base ➡️ insoluble salt + soluble salt
Write the balanced equation to show the formation of solid lead iodide from two solutions of lead nitrate and potassium iodide.
Pb(NO3)2(aq) + 2KI(aq) ➡️ Pbl2(s) + 2KNO3(aq)
Convert this into an ionic equation - remove any spectator ions
Pb2+(aq) +2l-(aq) ➡️ Pbl2(s)

Question 9

Water of crystallisation

Answer 9

In both examples, a crystalline salt is produced which is hydrated or chemically combined with water. This is called water of crystallisation, e.g CuSO4.5H2O
If the salt is heated to complete dryness, it will be anhydrous with no water, e.g CuSO4

Question 10

Define a hydrated substance

Answer 10

As a substance that is chemically combined with water and an anhydrous substance as a substance containing no water

Question 11

Solubility rules - nitrate

Answer 11

All nitrates are soluble

Question 12

Solubility rules - chloride

Answer 12

All chlorides are soluble except AgCl, PbCl2

Question 13

Solubility rules - sulfates

Answer 13

All sulfates are soluble except CaSO4, PbSO4, BaSO4

Question 14

Solubility rules hydroxides

Answer 14

All hydroxides are insoluble except those in group 1 and those of group 2 are slightly soluble

Question 15

Solubility rules - carbonates

Answer 15

All carbonates are insoluble except those of group 1 and (NH4)2CO3