Unit 4- Chemical Changes

Question 1

On the Ph scale what number are acids and what colour are they

Answer 1

0-6
Red to yellow

Question 2

On the Ph scale what number is neutral and what colours is it

Answer 2

7 - green

Question 3

On Ph scale what number and colour is alkalis

Answer 3

8-14
Blue to purple

Question 4

How do you measure Ph of a solution

Answer 4

Use an indicator will change colour depending on whether it’s above or below a certain Ph.

Question 5

What is the relation between acid and bases

Answer 5

They neutralise each other

Question 6

What is a base

Answer 6

Substance that will react with an acid to form a salt

Question 7

Equipment you will find in a titration experiment

Answer 7

Burette, conical flask with methyl orange, pipette

Question 8

What colour will phenolphthalein turn

Answer 8

Pink in alkali
Colourless in acid

Question 9

What colour will methyl orange turn

Answer 9

Red in acid
Yellow in alkali

Question 10

What colour will litmus turn

Answer 10

Red in acid
Blue in alkali

Question 11

What does a acid and metal oxide make

Answer 11

Salt and water

Question 12

What does salt and metal hydroxide make

Answer 12

Salt and water

Question 13

What do acids produce in water

Answer 13

Protons

Question 14

What type of reaction the ionisation of a weak acid

Answer 14

Reversible, equilibrium lies go the left

Question 15

What happens with weak acids in solution

Answer 15

Don’t fully ionise, only small portion release H ions

Question 16

What happens with strong acids in water

Answer 16

Ionise completely, dissociate to realise H ions

Question 17

For metals how is their reactivity determined

Answer 17

How easily they lose electrons forming positive ions

Question 18

What is the relativity series in order

Answer 18

Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper

Question 19

What does acid and metal make

Answer 19

Salt and hydrogen

Question 20

What is oxidation

Answer 20

gain of oxygen or loss of hydrogen
Negatively charged ions lose electrons at the Anode

Question 21

What is reduction

Answer 21

Positively charged ions gain electrons at the cathode
loss of oxygen or gain or hydrogen

Question 22

What is a redox reaction

Answer 22

a reaction in which both oxidation and reduction occur

Question 23

What is electrolysis

Answer 23

Splitting up compounds with electricity to form elements

Question 24

What is an electrolyte

Answer 24

A liquid or solution that conduct electricity

Question 25

What does electrolysis of molton ionic solids form

Answer 25

An element

Question 26

What is the positive electrode

Answer 26

Anode

Question 27

What is the negative electrode

Answer 27

Cathode

Question 28

Which electrode does positive metals go

Answer 28

Reduced at the cathode

Question 29

Which electrode do non metal ions go

Answer 29

Oxidised at the anode

Question 30

Why can ionic compound not undergo electrolysis

Answer 30

Because the ions are in fixed positions and can’t move

Question 31

Why is hydrogen chloride a gas at room temperature

Answer 31

Weak intermolecular forces

Question 32

What is an intermolecular force

Answer 32

Strong attractive force

Question 33

What is activation energy

Answer 33

Minimum amount of energy required for a chemical reaction to occur

Question 34

What does bond energy mean

Answer 34

Energy needed to break mole of particular bond

Question 35

Differences between the nuclear and plum pudding model

Answer 35

Plum pudding there is no empty spaces Electrons orbit the nucleus in nuclear model Mass of atom is in centre in plum pudding / evenly distributed in nuclear model

Question 36

Why does graphite conduct electricity

Answer 36

Each carbon atom forms 3 covalent bond one atom is delocalised and these electrons carry charge through graphite

Question 37

Explain why hydrogen chloride is a gas at room temperature

Answer 37

Hydrogen chloride is simple molecular so has weak intermolecular forces therefore requiring little energy to overcome

Question 38

Explain why you would not expect titanium chloride to be a liquid at room temp

Answer 38

Titanium chloride is ionic and metal chlorides have high melting points because they have strong electrostatic forces between ions

Question 39

Explain why an acid can be both strong and dilute

Answer 39

Strong because completely ionised Dilute because small amount of acid per unit volume

Question 40

Why should you use a polystyrene cup rather than a glass beaker

Answer 40

Polystyrene is a better insulator so reduced energy exchange with surroundings

Question 41

What two substances out of diamond, magnesium, polythene, sodium chloride and water have intermolecular forces

Answer 41

Water and polyethene

Question 42

What electrode do metals go to

Answer 42

Cathode

Question 43

What electrode does hydrogen go to

Answer 43

Cathode

Question 44

What does inert mean

Answer 44

Unreactive

Question 45

What element is used to reduce metal oxides and make pure metals

Answer 45

Carbon

Question 46

Acid + metal —>

Answer 46

Salt + hydrogen

Question 47

Acid + metal carbonate —>

Answer 47

Salt + water + carbon dioxide

Question 48

What do aqueous solutions of alkali contain

Answer 48

OH ions

Question 49

what happens to the ions in an ionic compound when melted or dissolved in water

Answer 49

The ions become free to move allowing them to conduct electricity

Question 50

What ions are discharged to produce oxygen at the positive electrode

Answer 50

Hydroxide ions (H plus and OH minus)

Question 51

Advantages of hydrogen fuel cells

Answer 51

No toxic chemicals to dispose at the end of cell life No loss of efficiency over time You can travel further before refuelling

Question 52

Disadvantages of extraction of metals using electrolysis

Answer 52

Very expensive because it requires a lot of energy and electricity

Question 53

When extracting metals when should you use electrolysis

Answer 53

If metal is more reactive than carbon

Question 54

What can metals be mixed with to lower melting point so they are ready for process of electrolysis

Answer 54

Cryolite, making it easier to melt and reducing the energy required for the electrolysis process

Question 55

Equation linking moles Concentration and volume

Answer 55

Moles =concentration x volume

Question 56

What is a neutralisation reaction

Answer 56

Acid and alkali react together

Question 57

What are the rules for electrolysis

Answer 57

1. The less reactive negative ion will be reduced at the cathode while the more reactive stays in the solution 2. If there is a halide ion (fluoride, bromide chloride) they are always oxidised at the anode (halogen gases are diatomic so remember for half equations ), if not oxygen is produced 3. the other ions stay in the solution so if sodium and hydroxide ions are left they makes sodium hydroxide

Question 58

What is the reactivity series in order

Answer 58

Potassium Sodium Lithium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Hydrogen Copper Silver Gold platinum

Question 59

What is produced at anode and cathode and give half equations for electrolysis of sodium chloride

Answer 59

Cathode = hydrogen reduced 2H+ + 2e- —> H2 Anode = chloride oxidised 2Cl—-> Cl2 + 2e- Sodium hydroxide left in solution

Question 60

What is produced at anode and cathode and give half equations for electrolysis of copper sulfate

Answer 60

Cathode = copper ions reduced Cu2+ +2e- —> Cu Anode = oxygen is oxidised 4OH- —> O2 + 2H2O + 4 e- Sulphuric acid left in solution

Question 61

What is produced at anode and cathode in electrolysis of molten compound aluminium oxide also give half equations

Answer 61

Cathode = aluminium reduced Al3+ + 3e- —> Al Anode = oxygen is oxidised 2O2- —> O2 +4e-