Electrolysis

Question 1

What is electrolysis?

Answer 1

The flow of charge by moving ions.

Question 2

What do the ions move through?

Answer 2

A molten ionic electrolyte.

Question 3

What reaction happens at the cathode during the electrolysis of NaCl?

Answer 3

• Na^+ + e^- —> Na
• The sodium chloride splits into ions so they are free to move
• The positive Na^+ ions migrate to the negative cathode
• Each Na^+ ion gains an electron from the cathode

Question 4

What reaction happens at the anode during the electrolysis of NaCl?

Answer 4

• 2Cl^- - 2e^- —> Cl2
• The negative Cl^- ions migrate to the positive anode
• Two Cl^- ions gain two electrons and are discharged as a chlorine gas molecule

Question 5

What products would be discharged at the anode and cathode during the electrolysis of NaOH?

Answer 5

Anode - oxygen, 4OH - 4e^- —> 2H2O + O2

Cathode - hydrogen, 2H^+ + 2e^- —> H2

Question 6

Why is hydrogen made rather than sodium at the cathode?

Answer 6

Sodium is higher up in the reactivity sequence so hydrogen is discharged in preference.

Question 7

What increases the amount of substance produced during electrolysis?

Answer 7

Time and current are directly proportional to how much substance is produced.