Electrochemistry Flashcards

1
Q

What happens when an electric current is passed through a molten ionic compound

A

The compound decomposes - this is called electrolysis

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2
Q

Do molten ionic componds in solution undergo electrolysis (decompositon of of the comound when electricuty is passed thought it.)?

A

Yes

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3
Q

Define electrolysis

A

The brakdown of an ionic compound (molten or in aqueous solution) by the passage of electricity.

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4
Q

what is the name of the vessel in which electrolysis takes place?

A

An electrolysis cell.

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5
Q

What equipment does eletroysis need?

A

power supply

anode (positve electrode)

Cathode (negative electrode)

Electrolyte (the molten / aqueous soltion of a compound)

Beaker

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6
Q

Define an electrorode

A

A rod of metal or graphite which leads an electric current to or from an electrolyte.

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7
Q
A
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8
Q

Electrolyte

A

An ionc compound which conducts electricity when molten or dissolved in water.

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9
Q

Define an anode

A

A positive electrode

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10
Q

Define a cathode.

A

A negative electrode.

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11
Q

Define an anion

A

A negative ion.

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12
Q

Define a cation.

A

A positive ion.

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13
Q

When molten lead bromide is the electrolyte what forms at the anode and cathode?

A

Anode: bromine

Cathode: lead

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14
Q

When dilute sulphuric acid is the electrolyte what forms at the anode and cathode?

A

Anode: oxygen

Cathode: hydrogen

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15
Q

When concentrated hydrochloric acid is the electrolyte what forms at the anode and cathode?

A

Anode: chlorine

Cathode: hydrogen

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16
Q

When concentrated acqueous sodium chloride is the electrolyte what forms at the anode and cathode?

A

Anode: chlorine

Cathode: hydrogen

17
Q

When molten zinc chloride is the electrolyte what forms at the anode and cathode?

A

Anode: chlorine

Cathode: zinc

18
Q

When molten sodium iodide is the electrolyte what forms at the anode and cathode?

A

Anode: iodine

Cathode: sodium

19
Q

What is an ionic half equation?

A

An equation balanced by electrons which shows either oxidation or reduction.

20
Q

Define electroplating

A

The coating of the surface of one metal with a layer of another by an electrolytic reaction.

21
Q

Define electrochemical cell

A

A source of electricalchemical energy where two metals of differnt reactivity dipping into an electrolyte are connected via an external circuit.

22
Q

What are the equations at the anode and cathode for

A

Cathode reaction: Pb2+ + 2e- becomes Pb

Anode reaction: 2Br- becomes Br2 +2e-

23
Q

What are the equations at the anode and cathode for concentrated aqueous NaCl?

A

Cathode reaction: 2H+ + 2e- becomes H2

Anode reaction: 2Cl- becomes Cl2 + 2e-

24
Q

What are the equations at the naode and cathode for dilute aqueous NaCl?

A

Cathode reaction: 2H+ + 2e- becomes H2

Anode reaction: 4OH- becomes O2 + 2H2O + 4e-

25
Q

What are the equations at the anode and cathode for concentrated aqueous CuSO4?

A

Cathode reaction: Cu2+ + 2e- becomes Cu

Anode reaction: 4OH- becomes O2 + 2H2O + 4e-

26
Q

What are the equations at the anode and cathode for concentrated aqueous HCl?

A

Cathode reaction: 2H+ +2E- becomes H2

Anode reaction: 2Cl- becomes Cl2 + 2e-

27
Q

What are the equations at the anode and cathode for dilute aqueous H2SO4?

A

Cathode reaction: 2H+ +2e- becomes H2

Anode reaction: 4OH- becomes O2 +2H2O + 4e-

28
Q

why can electrolysis only take place in molten or aqueous salts?

A

Molten salts:

Particles present are ions eletroysis can only take place when the salt is molten and so that the ions separate from each other and are free to move.

Aqueous solutions:

When salts dissolve in water they separate into their ions and are free to move.

29
Q

What are formed at the cathode (negative electrode):

metals and hydrogen.

This is because their ions are positively charged and opposites attract.

A

What are formed at the anode (positive electrode):

non metals.

This is because their ions are negatively charged and opposites attract.

30
Q

for compound formed of a metal and non metal which material goes to the anode and cathode?

A

metal goes to cathode

non metal goes to anode

31
Q

What is the term for the reaction at the anode?

A

A oxidation reaction because electrons are lost.

32
Q

What is the term for the reaction at the cathode?

A

A reduction reaction because electrons are gained.

33
Q

Does a anode have positive or negative charge?

A

Positive.

34
Q

Does a cathode have positive or negative charge?

A

Negative.

35
Q

What haapens when the anode is reactive?

A

The metal