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Chemistry > C6 Electrolysis > Flashcards

C6 Electrolysis Flashcards

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1
Q

why cannot solid ionic compounds cannot conduct electricity .

A

The ions are locked in place and are not free to move , they are held together by strong electrostatic forces of attraction .

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2
Q

Why can ionic compounds that are molten or dissolved in water conduct electricity ?

A

the forces of attraction are broken and the ions are free to move .

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3
Q

what are electrolytes

A

compound that is broken down by electrolysis and therefore can conduc electricity

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4
Q

what are the two ions n lead bromine

A

Pb2+ Br-

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5
Q

how many electrodes are in electrolysis

A

two

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6
Q

what are the electrodes made of

A

conducting materal such as graphite or a metal .

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7
Q

what is the negative electode

A

cathode

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8
Q

what is the positive electrode

A

anode

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9
Q

what happens pb2+ (lead) whta type of reaction is ths

A

the Pb+ gain two electrons from Pb atoms this is called Reduction
Pb—>pb2+ +2e-

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10
Q

what happens in reduction

A

u gain electrons

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11
Q

What happens to Br-

A

Br- looses oe electron to for Br atoms this is called oxidation

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12
Q

what happens in oxidiation

A

loose electrons

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13
Q

what is electrolysis

A

electrolysis is the breakdown of a substance conataining ions by electricity

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14
Q

how are metals less reactive than carbon extracted

A

metals less reactive than carbon cna be extracted by reduction with carbon .

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15
Q

how are metals more reactive than carbon extracted.

A

Metals more reactive than carbon can be extracted using electrolysis .

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16
Q

What does aluminium oxide contain

A

it contains aluminum ions (AL3+) and Oxide ions (02-)

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17
Q

why is aluminium oxide not produced by the electrolysis of an aqueous solution ?

A

As aluminium oxide is insoluble in water .

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18
Q

what is the first step of electrolysis with aluminium oxide

A

aluminium oxide is mixed with cryolite .

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19
Q

why is aluminium oxide mixed with cryolite

A

as it lowers the melting point of aluminium oxide as it as a high a very high melting point , reducing the amount of energy needed and saves money for electrolysis .

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20
Q

what are the anode and cathode made of and why ?

A

Made of graphite , as it is a very good conductor of electricity and has a very high melting point .

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21
Q

where are the AL3+ ions attracted to.

A

AL3+ ions are attracted to the cathode (the negative electrode .

22
Q

Give the half equation at the cathode for aluminium oxide what type of reaction is it and why

A

AL3+ + 3E- arrow AL - it is a reduction as each ion gains three electrons and forms aluminium atoms .

23
Q

Why is aluminium ions attracted to the negative elctorde

A

As aluminium ions are metals so are positively charged so are atracted to the negative electrode as opposites attract and gain three electrons ,

24
Q

where are oxide ions attracted to in alumnium oxide

A

02- ions are attracted to the anode (positive terminal)

25
Q

what is the half equation at the anode for aluminium oxide . What type or reaction is it and why

A

202-4e-arrowO2 it is oxidation as the oxide ions loses two electrons to form an oxygen atom .

26
Q

Why must the anode be replaced regularly

wrtie the equation for this .

A

as the oxygen molecules produced at the anode react with the graphite (carbon) , forming C02 gas .
c+02arrow co2

27
Q

why do u need to double everything at the anode for aluminium oxide

A

as oxygen atoms at the anode pair up up to form oxygen molecules .

28
Q

give two reasons why electrolysis is expensive

A
  • Melting the compounds such as aluminium oxide requires a great deal of energy .
  • A lot of energy is required to produce the electric current .
29
Q

Meaning of aqueous solutions

A

dissolved in water

30
Q

water molecules ionise (split) forming what ?

A

hydrogen ions H+

and hyrdoxide ions OH-

31
Q

what is the formula for Copper sulfate solution

A

CuSO4(aq)

32
Q

what does CuSO4 split into

A

CU2+
SO42-
and H+ -hydrogen ions and OH- hydroxide ions because aqueous

33
Q

What are the two possible things that can be produced at the cathode for copper sulfate solution .

A

Cu2+

or H+

34
Q

which one is porduced at the cathode at copper sulfate solution and why .

A

Hydrogen is produced at the cathode if the metal is more reactive than hydrogen .
Copper is less reactive than hydrogen os i produced

35
Q

What is produced at the anode for copper sulfate solution

A

oxygen gas , usually , when carrying out electrolysis on an aqueous solution , we usually get oxygen produced at the anode .

36
Q

Why should electrodes be inert

A

As it is important that electrodes do notg react witht he chemicals that were making an electrolysis .

37
Q

what is the meaning of inert

A

do not react .

38
Q

what material is often used as inert electrodes and why

A

platinum is ofen used as inert electrodes as platinum is a very unreactive material .

39
Q

What is the half equation at the cathode for copper sulfate solution

A

Cu2+ +2e- —> Cu

40
Q

what type of reaction is at the cathode for copper sulfate solution and why

A

it is a reduction as copper ions gain 2 electrons to become copper attoms .

41
Q

what is the half equation for the anode for copper sulfate solution and why . What type of reaction is it ?

A

40H—-> 02+ 2H20 + 4e-

hydroxide ions react to make oxygen and water and use 4 electrons in the process so it is an OXIDATION REACTION .

42
Q

What is the formula for sodium chloride

A

NaCl

43
Q

what two ions is sodium chloride made up of

A

Na+ sodium ions
and
Cl- and chloride ions
and H+-hrdogen ions and OH- hydroxide ions as it is in an aqueous solution .

44
Q

What are the two potential discharges at the cathode for sodium chloride

A

Na+ sodium ions

H+ hydrogen ions

45
Q

What is produced at the cathode for sodium chloride

A

Hydrogen is prooduced at the cathode if the metal is more reactive than hydrogen . Sodium is MORE reactive than hydrogen so HYDROGEN is produced at the CATHODE

46
Q

What are the two potential discharges at the anode for sodium chloride

A

Cl- chlorine ions

OH- hydroxide ions

47
Q

what is produced at the anode for sodium chloride

A

If the aqueous solution contains halide ions (Cl-,Br-,I-) then the halogen will be produced at the anode otherwise oxyegn .As the sodium chloride contains chloride ions , CHLORINE GAS will be produced at the ANODE .

48
Q

What is thehalf equation and reaction at the cathode for sodium chloride

A

2H+ + 2e —> H2
The hydrogen ion is gaining one electron to become a hyrdogen atom so is a REDUCTION . However hydrogen atoms pair to make hydrogen molecules so everything doubles .

49
Q

What is the half equation and reaction at the anode for sodium chloride

A

2CL- —>cL2 +2e-
The chloride ion looses one electron to form a chloride atom so it is an OXIDATION , however , chlorine atoms pair to form chlorine molecules so everything doubles .

50
Q

what is a positively charged ion called

A

cation

51
Q

what is a negatively charged ion called

A

anion

Chemistry (20 decks)

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