Acids and Bases (C4)

Question 1

What does pH measure?

Answer 1

Acidity or Alkalinity

Question 2

What is indicator?

Answer 2

A dye that changes colour depending on its pH

Question 3

Is pH 7 acid or alkali?

Answer 3

Neutral

Question 4

Is pH 5 acid or alkali?

Answer 4

Acid

Question 5

Is pH 9 acid or alkali?

Answer 5

Alkali

Question 6

Is pH 14 acid or alkali?

Answer 6

Strong Alkali

Question 7

Is pH 1 acid or alkali?

Answer 7

Strong Acid

Question 8

What can we use to judge pH?

Answer 8

pH probe or indicator

Question 9

Define Acid

Answer 9

Substances that form aqueous solutions with a pH below 7

They form H+ ions in water

Question 10

Define Base

Answer 10

A substance with a pH greater than 7

Question 11

Define Alkali

Answer 11

A base dissolved in water to form a solution greater than 7

Alkalis form OH- ions in water

Question 12

Neutralisation Reaction

Answer 12

Base + Acid = Water + Salt

BAWS

Question 13

Neutralisation Reaction in terms of ions

Answer 13

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

Question 14

What is titration for?

Answer 14

They allow you to find exactly how much acid is needed to neutralise an alkali or vie versa.

Question 15

What is the first step of a titrartion?

when you are finding the concentration of an alkali needed for the neutralisation of an acid

Answer 15

Use a pippette and pippette filler, add a set volume (25cm^3) of the alkali to a conical flask. Add a few drops of indicator.

Question 16

What is the second step of a titrartion?

when you are finding the concentration of an alkali needed for the neutralisation of an acid

Answer 16

Use a funnel to fill a burette with acid. Make sure you do this below eye level. Record the initial volume of the acid in the burette.

Question 17

What is the third step of a titrartion?

when you are finding the concentration of an alkali needed for the neutralisation of an acid

Answer 17

Add acid slowly from the burette into the conical flask, swirlig constantly until you see the end-point. This is visible when the colour changes.

Question 18

What is the fourth step of a titrartion?

when you are finding the concentration of an alkali needed for the neutralisation of an acid

Answer 18

Record the final volume of the acid in the burette and use it to calculate the volume of acid needed to neutralise the alkali.

Question 19

What should you do to increase the accuracy of your titration?

Answer 19

You should take several consstent results. Take only answers within 0.1cm^3 of each other and ignore any anomalous results.

Question 20

Why is universal indicator not ideal for titrations?

Answer 20

It changes colour gradually

Question 21

What indicators are best for titrations?

Answer 21

Single indicators

litmus, phenolphthalein, methyl organge

Question 22

What colour does litmus paper turn?

Answer 22

Blue in alkalis and red in acids.

Question 23

What colour does phenolphthalein turn?

Answer 23

Pink in alkalis and colourless in acids and neutral

Question 24

What colour does methyl orange turn?

Answer 24

Yellow in alkalis and red in acids

Question 25

What is a strong acid?

Answer 25

Fully ionising in an aqueous solution | They produce H+ hydrogen ions

Question 26

What is a weak acid?

Answer 26

Weak acids do not fully ionise in aqueous solutions. Only a small proportion of acid particles dissociate to release H+ ions.

Question 27

Examples of strong acids

Answer 27

Sulphuric Acid Hydrochloric Acid Nitric Acid

Question 28

Examples of weak acids

Answer 28

Ethanoic Acid Citroc Acid Carbonic Acid

Question 29

The ionisation of which acids is reversible?

Answer 29

Weak Acids

Question 30

What is pH?

Answer 30

Concentration of H+ ions

Question 31

If the concentration of H+ ions in an acid that was pH 4 is increased by a factor of 10, what is the pH now?

Answer 31

pH5

Question 32

Which has a higher pH, strong acid or weak acid?

Answer 32

Weak acid has a higher pH than strong acid

Question 33

Reaction between acid and metal oxide

Answer 33

``` Metal Oxide (Base) + Acid = Water + Salt BAWS ```

Question 34

Reaction between acid and metal hydoxide

Answer 34

``` Metal Hydroxide (Base) + Acid = Water + Salt BAWS ```

Question 35

What is salt produced in a reaction between hydrochloric acid and a metal?

Answer 35

Metal chloride

Question 36

What is salt produced in a reaction between sulphuric acid and a metal?

Answer 36

Metal sulphate

Question 37

What is salt produced in a reaction between nitric acid and a metal?

Answer 37

Metal nitrate

Question 38

Reaction between acid and metal carbonate

Answer 38

Metal Carbonate + Acid = Water + Carbon Dioxide + Salt | CAWCS

Question 39

Name 3 types of bases

Answer 39

Metal oxides Metal hydroxides Metal carbonates

Question 40

Which base does not form a BAWS reaction?

Answer 40

Metal Carbonates form a CAWCS reaction (with carbon dioxide)

Question 41

How do you make a soluble salt from an insoluble base?

Answer 41

- Gently warm the dilute acid on a bunson burner, then switch off - Add the base, stirring until it sinks to the bottom (it will be in excess at this point) - Filter out excess base - Gently heat the solution in a water bath or electric heater to evaporate water - Stop heating and allow to cool - Filter and dry the crystals

Question 42

What process seperates an insoluble?

Answer 42

Crystallisation

Question 43

What is the reactivity series?

Answer 43

Order of metal reactivity

Question 44

Which non-metals are in the reactivity series?

Answer 44

Hydrogen and Copper

Question 45

How reactive is Potassium (K)

Answer 45

Very

Question 46

How reactive is Copper (Cu)

Answer 46

Not very

Question 47

How reactive is Carbon (C)

Answer 47

Fairly

Question 48

How reactive is Lithium (Li)

Answer 48

Very

Question 49

How reactive is Hydrogen (H)

Answer 49

Not very

Question 50

How reactive is Sodium (Na)

Answer 50

Very

Question 51

How reactive is Magnesium (Mg)

Answer 51

Fairly

Question 52

How reactive is Iron (Fe)

Answer 52

Fairly

Question 53

How reactive is Calcium (Ca)

Answer 53

Very

Question 54

How reactive is Gold (Au)

Answer 54

Not - It's a native metal

Question 55

How reactive is Zinc (Zn)

Answer 55

Fairly

Question 56

Define Native Metal

Answer 56

Usually found in their pure form, pretty much unreactive

Question 57

What forms if an acid reacts with a metal?

Answer 57

Acid + Metal = Salt + Hydrogen

Question 58

Test for Hydrogen

Answer 58

Squeaky Pop test | Place a lit splint near it, you should hear a 'squeaky-pop-

Question 59

Which metals will readily undergo a reaction with acids?

Answer 59

Anything more reactive than hydrogen

Question 60

What forms if water reacts with a metal?

Answer 60

Metal + Water = Metal Hydroxide + Hydrogen

Question 61

Which metals will readily undergo a reaction with water?

Answer 61

Potassium (K) Sodium (Na) Lithium (Li) Calcium (Ca)

Question 62

Define Oxidation

Answer 62

(Gain of oxygen) | Loss of electrons

Question 63

Define Reduction

Answer 63

(Loss of oxygen) | Gain of electrons

Question 64

How do we extract metals with low reactivity from their ores?

Answer 64

Reduction using carbon | anything less reactive than carbon

Question 65

How do we extract metals with high reactivity from their ores?

Answer 65

Electrolysis | anything more reactive than carbon

Question 66

Why can highly reactive metals not be extracted with carbon?

Answer 66

This reduction is a displacement reaction, more reactive metals will not be displaced by carbon

Question 67

What type of reaction is reduction using carbon?

Answer 67

Displacement Reaction

Question 68

What is a displacement reation?

Answer 68

When a more reactive element takes the place of a less reactive one in a compound

Question 69

What is a redox reaction?

Answer 69

A reaction where electrons are transferred

Question 70

Oxygen is essential to an oxidation or reduction reaction. True or False?

Answer 70

False | Any electron loss or gain classifies as a reduction or oxidation

Question 71

What do we call an ion which does not change in a reaction?

Answer 71

Spectator ions

Question 72

Define Electrolysis

Answer 72

Using an electrical current to 'split' a metal compound into its elements

Question 73

Why must a metal compound be molten or aqueous during electrolysis?

Answer 73

So that the ions can move freely

Question 74

Where does the positive ion go during electrolysis?

Answer 74

Cathode (negative electrode)

Question 75

Where does the negative ion go during electrolysis?

Answer 75

Anode (positive electrode)

Question 76

What do we call the molten or aqueous solution during electrolysis?

Answer 76

Electrolyte

Question 77

What happens during electrolysis of a molten solution?

Answer 77

Two rods (electrodes) with electrical current are placed in the electolyte Metals (positive ions) are attracted to the negative electrode Non - metals (negative ions) are attracted to the positive electrode These can then be collected in their pure form

Question 78

What is used to lower the melting point of metal compounds such as aluminium oxide, to make a molten solution?

Answer 78

Cryolite

Question 79

What is aluminum ore called?

Answer 79

Bauxite

Question 80

What happens at the negative elctrode?

Answer 80

The positive metal ion is attracted to the negative electrode. Here it gains electrons (reduction) and becomes its element.

Question 81

What happens at the positive elctrode?

Answer 81

The negative non-metal ion is attracted to the positive electrode. Here it looses electrons (oxidation) and becomes its element.

Question 82

What additional ions are involved in the electrolysis of an aqueous solution?

Answer 82

H+ and OH-

Question 83

When does hydrogen form at the cathode?

Answer 83

Electrolysis of an aqueous solution if hydrogen is less reactive than the metal

Question 84

When does oxygen form at the annode?

Answer 84

Electrolysis of an aqueous solution if no halide ions are present (Cl2, Br2 etc..)