Topic 8 Acids, Bases And Salts

Question 1

Universal indicator at acidic, neutral and alkaline

Answer 1

Acidic - red
Neutral - green
Alkaline - purple

Question 2

Phenolphthalein indicator at acidic, neutral and alkaline

Answer 2

Acidic - colourless
Neutral - colourless
Alkaline - pink

Question 3

Methyl Orange indicator at acidic, neutral and alkaline

Answer 3

Acidic - red
Neutral - orange
Alkaline - yellow

Question 4

Red litmus paper at acidic, neutral and alkaline

Answer 4

Acidic - red
Neutral - red
Alkaline - blue

Question 5

Blue litmus at acidic, neutral and alkaline

Answer 5

Acidic - red
Neutral - blue
Alkaline - blue

Question 6

Where are strong acids on the PH scale

Answer 6

0-2. Examples are hydrochloric, sulfuric or nitric acid

Question 7

Where are weak acids on in the pH scale

Answer 7

3-6. Examples are ethanoic or carbonic

Question 8

Where is neutral on the pH scale

Answer 8

7

Question 9

Where are weak alkalis on the pH scale?

Answer 9

8-11. Examples are ammonia

Question 10

Where are strong alkalis on the pH scale

Answer 10

12-14. Examples are sodium hydroxide or potassium hydroxide

Question 11

What do acids produce when dissolved?

Answer 11

H+ (aq) ions. The higher the concentration of hydrogen ions, the stronger the acid is

Question 12

What do alkalis produce when dissolved?

Answer 12

OH- (aq) ions

Question 13

What do weak acids and alkalis do in water?

Answer 13

Only partially ionise

Question 14

What do strong acids and alkalis do in water?

Answer 14

Completely ionise

Question 15

Dilute

Answer 15

contains a Small number of particles dissolved per unit volume

Question 16

Concentration

Answer 16

A measure of the number of moles of acid/alkali molecules dissolved in 1dm3 of water. Measured in mol/dm3. The higher the concentration the more acid/alkali molecules that have been dissolved

Question 17

Neutralisation

Answer 17

The reaction between an acid and an alkali which produces salt and water

Question 18

What is the ionic equation for neturalisation

Answer 18

H+ (aq) + OH- (aq) = H2O (l)

Question 19

Is neutralisation an exothermic reaction?

Answer 19

Yes

Question 20

Base

Answer 20

Metal oxide/hydroxide which neutralises an acid

Question 21

Alkali

Answer 21

A soluble base

Question 22

Acid + metal =

Answer 22

Salt + hydrogen

Question 23

Acid + base =

Answer 23

Salt + water

Question 24

Acid + alkali =

Answer 24

Salt + water

Question 25

What are bases and alkali?

Answer 25

Oxides/hydroxides

Question 26

Acid + carbonate =

Answer 26

Salt + water + carbon dioxide

Question 27

Acid + hydrogencarbonate =

Answer 27

Salt + water + carbon dioxide

Question 28

Acid + ammonia =

Answer 28

Ammonium salt

Question 29

Salt

Answer 29

A compound formed when some or all of the hydrogen ions in an acid are replaced by metal/ammonium ions

Question 30

How to test for hydrogen gas

Answer 30

Apply a lighted splint - if hydrogen is present there will be a squeaky pop

Question 31

How to test for carbon dioxide?

Answer 31

Limewater will turn from colourless to milky/cloudy if carbon dioxide is present there

Question 32

Facts about group 1 and 2 salts

Answer 32

Most group 1 and 2, aluminium and zinc salts are white. Dissolved in water they give colourless solutions.

Question 33

What are transition metals? What do they look like?

Answer 33

They are metals between groups 2 and 3 and are generally coloured

Question 34

How do you prepare a salt from an acid and base?

Answer 34

1. Measure 25cm3 of dilute acid and place in beaker 2. Warm dilute acid. Do not allow to boil 3. Add the base and stir. Continue adding until there is no further reaction and the unreacted base is in excess at the bottom of the beaker 4. Allow to cool then filter the mixture and collect the filtrate in an evaporating basin 5. Heat the filtrate in the evaporating basin until half of it has evaporated (to make it more concentrated) 6. Allow basin to cool and crystals will form 7. When crystals have formed, dry between 2 pieces of filter paper/desiccator/low temperature oven

Question 35

What is the first method to prepare a salt from an acid and alkali (soluble base)?

Answer 35

1. Fill burette with acid 2. Using pipette and pipette filler place 25cm3 of alkali solution into a conical flask 3. Add 3 drops of phenolphthalein into the conical flask until solution turns pink 4. Add acid from the burette the into the conical flask, swirl gently 5. Stop adding acid when indicator turns colourless 6. Record volume by reading burette 7. The reaction is repeated for a more accurate result, then again without indicator and using the more accurate result of acid 8. Pour solution into evaporating basin 9. Heat gently until half of the solution remains 10. Leave to cool and crystallise, remove crystals and dry

Question 36

What is the second method to prepare a salt from an acid and alkali (soluble base)?

Answer 36

Follow steps 1-5 of first method: 1. Fill burette with acid 2. Using pipette and pipette filler place 25cm3 of alkali solution into a conical flask 3. Add 3 drops of phenolphthalein into the conical flask until solution turns pink 4. Add acid from the burette into the conical flask and swirl gently 5. Stop adding acid when indicator turns colourless Then: 6. Add 2 spatulas of decolourising charcoal to conical flask 7. Heat gently - do not boil 8. Allow to cool slightly, then filter mixture into evaporating basin 9. Heat again until half of the solution remains 10. Leave to cool and crystallise, remove crystals and dry