Aqueous Electrolysis

Question 1

Water molecules can break apart (dissociate) to form what?

Answer 1

H+ and OH- ions

Question 2

What happens if a halide ion (Cl-/Br-/I-) is present at the anode?

Answer 2

That element is produced as per normal.

Question 3

What happens if there is not a halide present at the anode?

Answer 3

O2 and H2O are produced.

Question 4

What is the half equation for when there is not a halide present at the anode?

Answer 4

4OH- -> O2 + 2H2O + 4e-

Question 5

What happens if there is a metal LESS reactive than hydrogen at the cathode?

Answer 5

That element is produced as per normal

Question 6

What happens if there is a metal MORE reactive than hydrogen at the cathode?

Answer 6

H2 is produced.

Question 7

What is the half-equation for when there is a metal more reactive than hydrogen at the cathode?

Answer 7

2H+ + 2e- -> H2

Question 8

What happens to the ions that did not react in aqueous electrolysis?

Answer 8

They remain leftover in the solution as a third product.

Question 9

What is observed at the aqueous electrolysis of NaCl and why?

Answer 9

Bubbles of pale green gas at the anode as chloride is a halide ion so it reacts with the anode. Bubbles of colourless gas at the anode as sodium is more reactive than hydrogen, so we get hydrogen instead.

Question 10

What is leftover in the aqueous electrolysis of NaCl and why?

Answer 10

Sodium hydroxide (NaOH) as the Na+ (from NaCl) and OH- ions (from H2O) did not react.

Question 10

What are the 2 observations of the aqueous electrolysis of CuSO4?

Answer 10

Bubbles of colourless gas at the anode as sulfate is not an halide ion so we get O2 and H2O instead. A pink-orange solid would be observed at the cathode as copper is less reactive than hydrogen so we get copper.

Question 11

What is leftover in the solution of the aqueous electrolysis of CuSO4 and why?

Answer 11

Sulfuric acid (H2SO4) as the SO4 2- (from CuSO4) and H+ ions (from H2O) did not react.