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GCSE Chem > Electrolysis > Flashcards

Electrolysis Flashcards

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1
Q

What must be present for a substance to conduct electricity?

A
  • There must be charged particles present.

- These charged particles must be free to move.

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2
Q

What are charged particles in Electrolysis?

A

Electrons or Ions

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3
Q

Why do metals conduct electricity?

A

Their Structure.

  • A lattice of positive ions surrounded by a sea of delocalised electrons.
  • The delocalised electrons are free to moves, so electricity can flow.
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4
Q

Do ionic compounds conduct electricity?

A

They don’t conduct electricity when a solid, however they can conduct when in a molten form or aqueous solution.

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5
Q

Why can’t ionic compounds conduct electricity when in solid form?

A

Because the ions are held tightly in the lattice, they are not free to move (they can only vibrate in place).

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6
Q

Why can an ionic compound conduct electricity when in a molten form or aqueous solution?

A

Because the ions are no longer held in a lattice and are free to move around.

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7
Q

What are in ionic compounds that allow electricity to flow?

A

(Positive and Negative) Ions

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8
Q

What are Cations?

A

Positive Ions

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9
Q

What are Anions?

A

Negative Ions

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10
Q

What is an acronym to remember the differences in Anode and Cathode?

A

PANiC

Positive (=) Anode, Negative, (is), Cathode

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11
Q

Give an example of an Ionic Compound:

A

Sodium Chloride

Potassium Iodide

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12
Q

What does it mean if an Ionic compound is molten?

A

It has been melted.

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13
Q

What does it mean if an Ionic compound is an aqueous solution?

A

It has been dissolved in water.

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14
Q

Define Electrolysis:

A

A chemical change caused by passing an electric current through a compound which is either molten or in solution.

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15
Q

Give examples of a covalent compound:

A

C6H14
CH4
CO2

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16
Q

Although there are some exceptions, covalent compounds cannot conduct electricity in any state or solution, explain why?

A

They consist of individual molecules, which have no overall electrical charge. Meaning that no charged particles can move around.
Also, all electrons are held tightly in the atoms or in bonds so that they are not able to move from molecule to molecule.

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17
Q

Name a covalent compound that is capable of conducting electrolysis.

A

Ammonia (reacting with water)

18
Q

What can be observed when metals conduct electricity?

And compared to when an Ionic compound conducts?

A

No considerable changes can be observed however the metal may heat up.

When ionic compounds conduct, a chemical reaction occurs.

19
Q

What is an electrolyte?

A

A liquid or solution that undergoes electrolysis.
All electrolytes contain ions and the movement of these ions is responsible for both the conduction of electricity and the chemical changes that take place

20
Q

What element is frequently used in electrodes? (and why?)

A

Graphite, a form of Carbon - because it conducts electricity and is fairly chemically inert.
(Platinum is often used also for the same reasons)

21
Q

What is the Anode?

A

The positive electrode.

22
Q

What is the Cathode?

A

The negative electrode.

23
Q

Is the current used in Electrolysis usually a A.C or D.C current? (and why?)

A

D.C -

If it were an A.C current then the Anode and Cathode would constantly be switching over.

24
Q

Although the actual size of the voltage is not critical, what is the usual size used?

A

6V or a battery/power pack.

25
Q

What is shown through half-equations.

A

The reaction at either the cathode or the anode. It shows both the Oxidation and Reduction reactions.

26
Q

What is an e^- ? (Used in half equations)

A

An electron.

27
Q

In Electrolysis, what is meant by the term Reduction?

A

Reduction occurs when something gains electrons.

28
Q

In Electrolysis, what is meant by the term Oxidation?

A

Oxidation occurs when something loses electrons.

29
Q

What is the acronym OILRIG for Electrolysis?

A 
Oxidation
Is
Loss (of electrons)
Reduction
Is
Gain (of electrons)
30
Q

Sometimes ions are said to be discharged, what does discharged mean?

A

Discharged is when the ions lose their charge.

31
Q

When does an ion become discharged?

A

When the ion gives up electron(s) to the electrode or receives electron(s) from it.
They are discharged at the electrodes.

32
Q

Is the following reaction a Reduction or Oxidation one?

Pb^2+ + 2e^- -> Pb

A

Reduction, the Lead(II) ions are gaining electrons.

33
Q

Generally which reaction occurs at the Cathode, and which occurs at the Anode?

A 
Cathode = Reduction
Anode = Oxidation
34
Q

What is a REDOX reaction?

A

A reaction where Reduction and Oxidation occur at the same time.

35
Q

What does REDOX stand for?

A

RED(uction)OX(idation)

36
Q

What is required in the balancing of half equations?

A

Each side of the equation must have the same number of atoms (not including electrons)
Each side must have the same charges on ions

37
Q

What assumption can be made when electrolysis a molten ionic compound containing two elements?

A

The metal will form at the cathode (because metals form positive ions). The non-metal will form at the anode (because non-metals form negative ions).

38
Q

Why are positive ions called Cations?

A

Because they are attracted to the cathode.

39
Q

Why are negative ions called Anions?

A

Because they are attracted to the anode.

40
Q

Not all ionic compounds can be electrolysis when they are molten. What happens to those that cannot be electrolysed?

A

They break up into simpler substances before their melting point.

41
Q

How do you set up an electrochemial cell for Electrolysis?

A

1) Find two inert electrodes eg. Carbon or Platinum.
2) Clean the electrodes with emery paper (or sandpaper).
3) Place both electrodes in a beaker filled with the electrolyte.
4) Connect the electrodes to a power supply using crocodile clips and wires. When turned on, a current will flow through the cell.

GCSE Chem (19 decks)

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