C6 - Electrolysis

Question 1

What are Ionic Equations

Answer 1

Equations that only show the atoms and ions that change in a reaction

Question 2

What is the definition of electrolysis

Answer 2

The splitting up of compounds using electricity

Question 3

How do you set up a circuit for electrolysis

Answer 3

Dip two electrodes in the electrolyte with a gap in between, connected to a power supply

Question 4

What is the positive electrode called

Answer 4

Anode

Question 5

What is the negative electrons called

Answer 5

Cathode

Question 6

What are the electrodes made of

Answer 6

Unreactive (inert) substances, such as graphite, so they don’t react with the electrolyte or the products

Question 7

What moves to the anode and what moves to the cathode

Answer 7

Negatively charged ions (non-metals) move to the anode and positively charged ions (metals) move to the cathode

Question 8

What happens at the anode

Answer 8

Oxidation as negative ions lose electrons to become neutral atoms

Question 9

What happens at the cathode

Answer 9

Reduction as positively charged ions gain electrons to become neutral atoms

Question 10

Why are 4 ions present in aqueous solutions

Answer 10

There are 2 ions present from the compound and H+ and OH- ions present from the water

Question 11

What are the rules of aqueous solutions at the anode

Answer 11

If the -Ions are halogens then the halogen is produced (discharged). If the -Ions are not halogens then oxygen is produced (discharged from hydroxide ions)

Question 12

What are the rules for aqueous solutions at the cathode?

Answer 12

If the +ions are more reactive than hydrogen then hydrogen is produced (metal displaces into solution). If the +ions are less reactive that hydrogen then the metal is produced

Question 13

What is aluminium oxide mixed with for electrolysis and why?

Answer 13

Aluminium oxide is mixed with molten cryolite to lower the melting point to reduce costs for electrolysis

Question 14

What happens at the anode during the electrolysis of Aluminium oxide

Answer 14

Negative O2 ions are attracted to the anode where they each lose 2 electrons and then combine to form neutral O2 molecules and are produced as oxygen gas

Question 15

What happens at the cathode during the electrolysis of Aluminium Oxide

Answer 15

Positive aluminium 3+ ions are attracted to the cathode where they reduce to gain 3 electrons and form neutral aluminium atoms which sink to the bottom of the electrolysis cell and are collected from the cell

Question 16

What happens to the oxygen because of the carbon rods

Answer 16

The oxygen produced reacts with the hot ion electrodes to produce carbon dioxide gas and this means that the carbon anodes burn away and need to be replaced regularly

Question 17

What ions are present in the electrolysis of Sodium Chloride

Answer 17

Na+, Cl- , OH- , H+

Question 18

What happens at the cathode during the electrolysis of sodium chloride

Answer 18

Sodium and Hydrogen positive ions are attracted to the cathode. Sodium metal is more reactive than hydrogen so displaces it in the solution and hydrogen gas is produced (discharged)

Question 19

What happens at the anode during the electrolysis of Sodium Chloride

Answer 19

Chloride and Hydroxide ions are attracted to the anode. Chloride is discharged as it is a halogen which produces bubbles of pale green gas and OH- is left in the solution

Question 20

What are the end products of the electrolysis of Sodium Chloride and their uses

Answer 20

• Chlorine - used to disinfect swimming pools and make PVC
• Hydrogen - used as a fuel and in making margarine
• Sodium Hydroxide - used to make soap and other chemicals

Question 21

How do you test for chlorine gas?

Answer 21

Chlorine bleached damp litmus paper, turning it white

Question 22

How do you test for Hydrogen gas

Answer 22

Hydrogen gas makes a ‘squeaky pop’ with a lighted splint

Question 23

How do you test of oxygen

Answer 23

Oxygen gas will relight a glowing splint