Electrolysis

Question 1

how do you set up a general electrolysis experiment

Answer 1

• place anode and cathode in beaker containing molten or dissolved ionic compound
• connect both electrodes to a power supply with wires

Question 2

how could you investigate what happens when an aqueous solution on CuCl2 is electrolysed

Answer 2

• half fill a beaker with aqueous CuCl2
• place a lid on the beaker and insert the electrodes into the solution through the holes in the lid (electrodes mus not touch)
• connect the electrodes to a low voltage power supply -around 4V
• turn off the power after a few minutes and record any observations

Question 3

what forms at the cathode and anode in electrolysis

Answer 3

cathode: metal or hydrogen
anode: non-metals

Question 4

what would you observe at each electrode when copper chloride solution is electrolysed

Answer 4

anode: bubbles of gas (chlorine)
cathode: electrode coated with a brown solid, copper

Question 5

what would you observe at each electrode when sodium chloride solution is electrolysed

Answer 5

anode: bubbles of gas (chlorine)
cathode: bubbles of gas rapidly produces, hydrogen

Question 6

why must anode be constantly replaced

Answer 6

the positive electrode is made of carbon and will react with oxygen to produce carbon dioxide

Question 7

write a half equation for when CuCL2 is electrolysed

Answer 7

cathode: Cu2+ + 2e- => Cu

anode: 2Cl2- => Cl2 + 2e-

Question 8

in electrolysis of NaCL hydrogen is produced at the cathode, why isn’t sodium?

Answer 8

hydrogen is produced as it’s more reactive than hydrogen, sodium remains in the solution

Question 9

how could you test that chlorine gas was produced at the cathode

Answer 9

gas will bleach damp litmus paper - it will turn white

Question 10

how could you tell hydrogen gas is produced at the anode

Answer 10

the gas produced will make a squeaky pop with a lighted splint

Question 11

how could you tell oxygen is produced at the anode

Answer 11

it will relight a glowing splint