Electrochemistry

Question 1

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

Answer 1

The compound decomposes - this is called electrolysis

Question 2

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

Answer 2

Yes

Question 3

Define electrolysis

Answer 3

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

Question 4

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

Answer 4

An electrolysis cell.

Question 5

What equipment does eletroysis need?

Answer 5

power supply

anode (positve electrode)

Cathode (negative electrode)

Electrolyte (the molten / aqueous soltion of a compound)

Beaker

Question 6

Define an electrorode

Answer 6

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

Question 8

Electrolyte

Answer 8

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

Question 9

Define an anode

Answer 9

A positive electrode

Question 10

Define a cathode.

Answer 10

A negative electrode.

Question 11

Define an anion

Answer 11

A negative ion.

Question 12

Define a cation.

Answer 12

A positive ion.

Question 13

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

Answer 13

Anode: bromine

Cathode: lead

Question 14

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

Answer 14

Anode: oxygen

Cathode: hydrogen

Question 15

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

Answer 15

Anode: chlorine

Cathode: hydrogen

Question 16

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

Answer 16

Anode: chlorine

Cathode: hydrogen

Question 17

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

Answer 17

Anode: chlorine

Cathode: zinc

Question 18

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

Answer 18

Anode: iodine

Cathode: sodium

Question 19

What is an ionic half equation?

Answer 19

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

Question 20

Define electroplating

Answer 20

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

Question 21

Define electrochemical cell

Answer 21

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

Question 22

What are the equations at the anode and cathode for

Answer 22

Cathode reaction: Pb²⁺ + 2e^- becomes Pb

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

Question 23

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

Answer 23

Cathode reaction: 2H⁺ + 2e^- becomes H_²

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

Question 24

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

Answer 24

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

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

Question 25

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

Answer 25

Cathode reaction: Cu²⁺ + 2e^- becomes Cu Anode reaction: 4OH^- becomes O₂ + 2H₂O + 4e^-

Question 26

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

Answer 26

Cathode reaction: 2H⁺ +2E^- becomes H₂ Anode reaction: 2Cl^- becomes Cl₂ + 2e^-

Question 27

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

Answer 27

Cathode reaction: 2H⁺ +2e^- becomes H₂ Anode reaction: 4OH^- becomes O₂ +2H₂O + 4e^-

Question 28

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

Answer 28

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.

Question 29

What are formed at the cathode (negative electrode): metals and hydrogen. This is because their ions are positively charged and opposites attract.

Answer 29

What are formed at the anode (positive electrode): non metals. This is because their ions are negatively charged and opposites attract.

Question 30

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

Answer 30

metal goes to cathode non metal goes to anode

Question 31

What is the term for the reaction at the anode?

Answer 31

A oxidation reaction because electrons are lost.

Question 32

What is the term for the reaction at the cathode?

Answer 32

A reduction reaction because electrons are gained.

Question 33

Does a anode have positive or negative charge?

Answer 33

Positive.

Question 34

Does a cathode have positive or negative charge?

Answer 34

Negative.

Question 35

What haapens when the anode is reactive?

Answer 35

The metal