Acids Base and Salt Preparation

Question 1

universal indicator

Answer 1

use a chart

Question 2

litmus paper

Answer 2

• acidic = red
• neutral = purple
• alkaline = blue

Question 3

phenolphthalein

Answer 3

• acidic = colourless

- alkaline = pink

Question 4

Methyl orange

Answer 4

• acidic = red

- alkaline = yellow

Question 5

acids

Answer 5

source of H+ (hydrogen) ions. they are proton DONORS. pH of less than 7

Question 6

alkalis

Answer 6

soluble bases. source of HYROXIDE IONS (OH-). pH greater than 7

Question 7

neutralisation

Answer 7

reaction between acid and base = neutralisations. can also be seen as proton transfer. produces WATER

Question 8

titration

Answer 8

allow you to find out EXACTLY how much acid is needed to neutralise a quantity of alkali (or vice versa).

1. using a pipette and a pipette filler, add some alkali (25cm3) to a conical flask, along with 2 or 3 drops of indicator
2. fill a burette with the acid.
3. using the burette add the acid to the alkali a bit at a time, giving the conical flask a regular swirl
4. the indicator changes colour when all the alkali has been neutralised
5. record the volume of acid used to neutralise the alkali and repeat.

Question 9

rules of solubility

Answer 9

SOLUBLE :

• all common sodium, potassium and ammonium compounds
• all nitrates
• common chlorides (except 2)
• common sulphate (except 3)

INSOLUBLE

• common carbonates
• all hydroxides (except sodium, potassium and calcium ones)
• silver and lead chlorides
• lead, barium and calcium sulphates

Question 10

acid + metal oxide reaction

Answer 10

acid + metal oxide —> salt + water

Question 11

acid + metal hydroxide reaction

Answer 11

acid + metal hydroxide —> salt + water

Question 12

acid + ammonia reaction

Answer 12

acid + ammonia —> ammonium salt

Question 13

acid + metal carbonate reaction

Answer 13

acid + metal carbonate —> salt + water + carbon dioxide

Question 14

the type of salt formed depends on…

Answer 14

the acid used.

1. hydrochloric acid = chloride salts
2. sulphuric acid = sulphate salts
3. nitric acid = nitrate salts

Question 15

making insoluble salts

Answer 15

PRECIPITATION REACTION. eg. making lead sulphate.

1. add one spatula of lead nitrate to a test tube. add water to dissolve it. shake to make sure all has dissolved. in a separate test tube do the same with magnesium sulphate.
2. tip the 2 solutions into a small beaker and stir. the lead sulphate should PRECIPITATE out.
3. put a folded piece of filter paper into a filter funnel and put that in a conical flask
4. pour the contents of the beaker into the filter paper.
5. wash the paper with deionised water to wash away all soluble magnesium nitrate.
6. scrape the lead sulphate onto fresh filter paper to dry.

Question 16

making soluble salts

Answer 16

• by reacting an acid that contains one of the ions you want, with an insoluble base that contains the other ions you need.
  1. heat the acid in a water bath (speeds up reaction)
  2. add the base to acid - they will react to produce a soluble salt (and water). you will know when the base is in excess and all the acid has been neutralised becaus the excess solid will sink to the bottom.
  3. filter off the excess solid to get a solution containing only salt and water
  4. heat the solution gently using a bunsen burner to slowly evaporate off some of the water. leave the solution to cool and allow salt to crystallise.

Question 17

making soluble salts with acids/alkali reactions

Answer 17

• react an acid with an alkali

- use titration

Question 18

copper oxide to make hydrated copper (II) sulphate

Answer 18

add copper oxide to warm sulphuric acid to make a copper sulphate solution.

if you evaporate off some of the water and leave this solution to crystallise, you should get blue crystals of HYDRATED COPPER (II) SULPHATE