Separation Methods

Question 0

If the salt wanted is insoluble use…

Answer 0

Precipitation

Question 1

If the salt wanted is binary and anhydrous use…

Answer 1

Direct combination

Question 2

If the salt wanted contains a MAZIL metal use…

Answer 2

Excess metal + acid

Question 3

If the metal oxide/carbonate is insoluble use…

Answer 3

Excess insoluble base + acid

Question 4

If the metal oxide/carbonate is soluble use…

Answer 4

Titration (Soluble base + acid)

Question 5

What metals are MAZIL metals?

Answer 5

Mg, Al, Zn, Fe, Pb

Question 6

Describe the 3 steps in filtration.

Answer 6

1. Mix/stir the reactants together and filter off the precipitate. (Solid precipitate wanted will be in the filter paper)
2. Wash precipitate with distiller water to remove any remaining soluble impurities.
3. Dry the product in a warm oven to remove water.

Question 7

How can you use precipitation to work out the concentration of an ion in a solution?

Answer 7

1. Accurately measure the volume of the solution whose concentration is needed.
2. Precipitate out an ion by reacting with known chemical. Filter/dry as before in precipitation method.
3. Weigh product. Use equation:
   Concentration of ion= moles of ion/volume of solution it was in.

Question 8

Describe the 4 steps of excess metal + acid.

Answer 8

1. Add excess metal in stages to the acid to make sure that all the acid reacts
2. Stir and heat gently with AZIL metals to speed up the rate of reaction.
3. Filter off excess unreacted metal.
4. Obtain the crystals from a solution of the salt (crystallisation method)

Question 9

Describe the 4 steps of excess insoluble base/carbonate + acid.

Answer 9

1. Add excess insoluble base/carbonate in stages to the acid to make sure that all the acid reacts
2. Stir and heat gently with insoluble oxides/hydroxides to speed up the rate of reaction.
3. Filter off excess unreacted insoluble base/carbonate.
4. Obtain the crystals from a solution of the salt (crystallisation method)

Question 10

Explain ‘How to obtain crystals from a solution of the salt’.

Answer 10

1. Warm gently to evaporate some of the water, until a saturated solution is formed. You can tell that the solution is saturated when the first crystals appear.
2. Allow to cool and crystallise.
3. Dry crystals by pressing between filterpaper.

Question 11

Why when trying to obtain crystals from a solution the salt, do you not heat till dryness?

Answer 11

As the waters of crystalisation are lost and the product and thermally decompose

Question 12

Describe the 7 steps of titration. (NEUTRALISATION: Acid + Alkali -> Salt + Water)

Answer 12

1. Use a graduated pipette to measure out an accurate volume of alkali into a conical flask.
2. Add a few drops of Phenolphthalein indicator to the conical flask. It is pink in alkali and colourless in acid.
3. Place acid into your burette and note initial volume.
4. Add small amounts of acid, mixing frequently, so that one drop changes the indicator colour for accurate neutralisation volume. Read final acid volume on burette.
5. Repeat to check accuracy of volume of acid needed to neutralise alkali.
6. Repeat without indicator present but with the same volumes of acid and alkali, so that final product is pure.
7. Obtain the crystals from a solution of the salt