Electrolysis 2

Question 1

What happens during copper sulfate electrolysis

Answer 1

1) copper ions CU2+ will go into the electrolyte solution of copper sulfate
2) the CU2+ ions will be attracted to the cathode and pure copper will form

CU2*(aq) + 2E- = CU(s)

Question 2

when is the purification process complete

Answer 2

the purification process is complete when the mass of the cathode is constant

Question 3

how do you measure the mass of copper formed

Answer 3

1) Record the initial mass of the electrodes. the cathode must be clean for the copper to stick
2) use a variable resistor because the current may vary during the process

Question 4

what’s the equation for change of mass

Answer 4

change of mass = final mass - initial mass

Question 5

why is the electrolysis of aqueous solutions more complex

Answer 5

they are more complex as you have to consider the water

Question 6

what is formed in aqueous sodium chloride ( NaCl )

Answer 6

Hydrogen is formed instead of sodium

Question 7

what does applying electricity across aqueous sodium chloride ( NaCl ) produce

Answer 7

produces hydrogen gas at the CATHODE

produces chlorine gas at the ANODE

Question 8

what are the electrodes made out of when involving aqueous solutions ( NaCl )

Answer 8

the electrodes are made out of inert graphite or platinum

Question 9

in electrolysis of the aqueous solution ( NaCl ) the formation of hydrogen at the cathode can be detected using what

Answer 9

a lit splint, a squeaky pop will be heard if hydrogen is present

Question 10

in electrolysis of the aqueous solutions ( NaCl ) how can you detect the presence of chlorine

Answer 10

you can smell it

it turns bleaches the litmus paper

Question 11

what is produced when dilute sulphuric acid is electrolysed ( H2S04 )

Answer 11

Hydrogen is produced from the acid and oxygen in the water

Question 12

What Is produced at the anode and cathode when electricity is applied with graphite electrodes ( H2304 )

Answer 12

Hydrogen gas at CATHODE

Oxygen at ANODE

Question 13

How can you detect the presence of oxygen at the anode (H2S04)

Answer 13

glowing splint, splint will re-ignite/glow in tube if oxygen is present

Question 14

what is formed when graphite electrodes are used to apply electricity across molten lead bromide (PbBr2)

Answer 14

Lead metal at the CATHODE

Bromine at the ANODE

Question 15

How do you know if lead is present (PbBr2)

Answer 15

If a shiny metal forms around the cathode

Question 16

what is bromine observed as and why (PbBr2)

Answer 16

bromine is observed as a brown gas because of the high temperatures reached during the process

Question 17

what is produced when electricity is applied across hydrochloric acid with graphite electrodes (HCL) at the anode and cathode

Answer 17

Hydrogen gas at the CATHODE (Metal)

Chlorine gas at the anode (Gas)

Question 18

What are the half equations for the electrolysis of lead bromide (PbBr2)?

Answer 18

ANODE: 2Br− → Br2 + 2e−

CATHODE: Pb2+ + 2e− → Pb