C6 Electrolysis Flashcards

1
Q

What does electrolysis mean?

A

Breaking down using electricity

An electric current breaks down an ionic compound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is an electrolyte?

A

The compound broken down by electrolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens during electrolysis

A

Positively charged ions move to the cathode

Negative ions move to the anode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How you set up the electrical circuit for electrolysis?

A

Two electrodes are dipped in the electrolyte with a gap between
These act as conducting rods
One is connected to the positive terminal and is the anode
The other is connected to the negative terminal and is the cathode
Electrodes usually made of an un reactive substance (inert) eg graphite so electrodes do not react with the electrolyte or products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What happens when ions reach the electrodes

A

They lose their charge and become elements
As elements they may turn to gas or metal deposits
Depends on the compound and it maybe molten

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Explain electrolysis of zinc chloride

A

Zinc chloride is molten because as solid it will not conduct electricity
Zinc forms and deposits form at cathode
Chlorine gas given off at anode
Beware chlorine is toxic - wear safety mask.
Zncl2 (l)->Zn(s/l)+cl2(g)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What alternative is there to using molten ionic compounds

A

Some ionic substances dissolve in water releasing their electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What also happens with ionic compounds dissolved in water

A

The water also forms ions
Only metals below hydrogen in reactivity series are deposited from aqueous solutions
Eg copper (II) bromide : Cu2+ ions go to cathode Br- ions go to anode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What happens with covalent compounds

A

Covalent compounds cannot usually be electrolysed unless they ionise in water
Acids in water contain H+ (aq) ions plus negatively charged aqueous ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is reduction and give 2 examples of half equations?

A

Reduction is the gain of electrons
Na+ + e- ->Na
Al3+ + 3e- -> Al

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is oxidation and give 2 examples of half equations?

A

Loss of electrons
2Cl- -> Cl2 + 2e-
2O2- -> O2 + 4e-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the uses of aluminium

A
Trains
Planes
Foil
Cars
Drink cans
Window frames
Bicycle frames
Power cables
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why is aluminium extracted by electrolysis

A

Very reactive

More reactive than carbon so it can’t be displaced by it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is aluminium extracted from

A

Aluminium oxide which is also called alumina which has been purified from bauxite
It is mixed with molten cryolite to lower its melting point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens in electrolysis and what is the equation

A

Aluminium oxide -> aluminium + oxygen
Aluminium forms at the cathode - Al3+ + 3e- -> Al - redcuction
Oxygen at the anode 2O2- -> O2 + 4e- oxidation
It is a continuous reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens with the anodes

A

Oxygen reacts with carbon to make carbon dioxide

So carbon anodes burn away and need replacing

17
Q

In electrolysis of aqueous solutions what happens if the metal is more reactive than hydrogen

A
Electrolysis will produce hydrogen not the metal eg
Potassium chloride produces hydrogen
Sodium bromide produces hydrogen
Zinc chloride produces hydrogen 
But
Copper sulphate produce copper
Silver nitrate produces silver
18
Q

What is produced along in electrolysis of aqueous solutions ?
And why?

A

Ions that make the ionic compound
H+ (hydrogen) ions
OH- (hydroxide) ions
Due to partial ionisation of water

19
Q

What is a halogen

A

Flourine, chlorine, iodine, bromine, astatine
Reactive non metallic elements
Form strongly acidic compounds with hydrogen from which simple salts are made

20
Q

If a halogen is present what happens

A

The halogen will be produced at the anode
Eg potassium chloride produces chlorine
Eg sodium bromide produces bromine

21
Q

If no halogen is present what happens

A

Oxygen is formed

Eg copper sulphate produces oxygen at the anode
Eg silver nitrate produces oxygen

22
Q

What is chlorine used for

A

To kill bacteria in swimming pools

23
Q

Why must ionic compounds be molten or dissolved for electrolysis

A

They must be must molten so electrons are free and ions can move and carry charge

24
Q

What happens at the electrodes?

A

Ions are discharged

They gain or lose electrons so have no charge