Electrolysis Flashcards

1
Q

what is electrolysis?

A

a process that uses an electric current to split up a substance that contains ions

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2
Q

what type of substance is electrolysis often used to break down?

A

ionic compounds.

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3
Q

what had to be done to a solid ionic compound before it can be put through electrolysis?

A

an ionic compound has to be in a molten or aqueous form to be electrolysised because as a solid, ionic compounds don’t conduct electricity.

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4
Q

what is the name of a substance broken down by electrolysis?

A

an electrolyte

e.g lead bromide

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5
Q

what is the positive electrode called?

A

anode

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6
Q

what is the negative electrode called?

A

cathode

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7
Q

what is the equasions for e.g cl^(-)

A

2cl^(-) > cl(2) + 2e

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8
Q

what is the equasion for e.g cu^(2+)?

A

cu^(2+) + 2e^(-) > cu

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9
Q

what is an anion?

A

a negative ion

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10
Q

what is a cation?

A

positive ion

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11
Q

what is oxidation?

A

the loss of electrons

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12
Q

what is reduction?

A

the gain of electrons

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13
Q

what is often used for electrodes and why?

A

graphite

  • it’s unreactive
  • it conducts electricity
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14
Q

if molten magnesium oxide is electrolysed

which ions go to the positive electrode and why?

A
  • the negative ions because opposites attract

- (oxygen)

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15
Q

is e.g 2O^(2+) > O^(2) + 4e^(-)

oxidation or reduction?

A

oxidation- the loss of electrons

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16
Q

when molten magnesium oxide is electrolysed what forms at the cathode?

A

magnesium

17
Q

what is a halogen?

A

a group 7 element

18
Q

why is the rule for predicting the product at the positive electrode?

A

if the -ve ions are halogens then they are formed, otherwise oxygen will be formed.

19
Q

what is the rule for predicting the product at the negative electrode?

A

if the +ve ions are less reactive than hydrogen then they are formed, otherwise hydrogen is formed.

20
Q

what is a use of hydrogen?

A

used in the manufacture of margarine

21
Q

describe the test for hydrogen gas?

A

when hydrogen is present a squeaky pop will be heard in the presence of a little spling

22
Q

describe the test for chlorine gas

A

it makes damp litmus paper turn red and then bleaches it white

23
Q

what does purple UI indicate?

A

alkaline solution (ph 8-14)

24
Q

what does green UI indicate?

A

neutral solution (ph 7)

25
Q

what does red UI indicate?

A

acidic solution (6-1)

26
Q

what is electroplating?

A

when an object has been coated with a thin layer of metal by electrolysis

27
Q

give 2 reasons why something might be electroplated

A
  • to make it less corrosive

- harder

28
Q

why does graphite conducts electricity?

A

each carbon atom only has 3 bonds to other carbon atoms, leaving 1 delocalised electron per carbon atoms.

29
Q

define electrolyte

A

the substance broken down by electrolysis

30
Q

define electrode

A

the material that carries an electrical current

31
Q

name 3 products formed form the electrolysis of brine

A
  • chlorine
  • bleach
  • hydrogen