Aqueous Electrolysis

Question 1

what happens to ions in water?

Answer 1

water molecules can break apart to form H+ and OH- ions

Question 2

what happens at the anode at aqueous electrolysis?

Answer 2

• if a halide ion (Cl-/Br-/I-) is present, that element is produced as per normal
• otherwise, O2 and H2O are produced according the following half equation: 4OH- -> O2 + 2H2O + 4e-

Question 3

what happens at the cathode at aqueous electrolysis?

Answer 3

• if the metal is less reactive than hydrogen, that element is produced as per normal
• otherwise, H2 is produced according to the following half-equation: 2H+ + 2e- -> H2

Question 4

what happens to the ions that did not react in electrolysis?

Answer 4

they remain leftover as a third product

Question 5

during the aqueous electrolysis of NaCl what happens at the anode?

Answer 5

• chloride (Cl-) is a halide ion, so it reacts at the anode
• bubbles of place green gas would be observed

Question 6

during the aqueous electrolysis of NaCl what happens at the cathode?

Answer 6

• sodium (Na) is more reactive than hydrogen (H2), so we get hydrogen instead
• bubbles of colourless gas would be observed

Question 7

in the aqueous electrolysis of NaCl what is leftover in the solution?

Answer 7

the Na+ from the NaCl and OH- ions from H2O didn’t react
- sodium hydroxide (NaOH) is leftover

Question 8

in the aqueous electrolysis of CuSO4 what happens at the anode?

Answer 8

• sulfate (SO42-) is not a halide ion, so instead we get O2 and H2O
• bubbles of colourless gas would be observed

Question 9

in the aqueous electrolysis of CuSO4 what happens at the cathode?

Answer 9

• copper (Cu) is less reactive than hydrogen (H2) so we get coper
• a pink orange solid would be observed

Question 10

in the aqueous electrolysis of CuSO4 what is leftover in the solution?

Answer 10

• the SO42- from CuSO4 and H+ ions from H2O didn’t react
• sulfuric acid (H2SO4) is leftover