Electrolysis

Question 1

Why do covalent compound not conduct electricity?

Answer 1

No charged particles are free to move

Question 2

Why do ionic compounds conduct electricity when molten or in aqueous solution?

Answer 2

Ions are free to move

Question 3

Anion

Answer 3

Negative ion

Question 4

Cation

Answer 4

Positive ion

Question 5

How to investigate the electrolysis of aqueous solutions?

Answer 5

1. Set up the apparatus as shown
2. Pour concentrated solution into the glass tube
3. Place test tubes over each electrode without fully covering them
4. Connect the battery
5. Do the experiment in a fume cupboard as chlorine gas is poisonous

Question 6

What occurs in the electrolysis of molten compounds?

Answer 6

• Bulb lights up, showing that electrons are flowing through it
• There is bubbling around the anode connected to the positive terminal of the power source as gas is given off
• Solid metal is formed at the cathode

Question 7

How is hydrogen produced in electrolysis of aqueous solutions?

Answer 7

H₂O <-> H⁺ + OH^-
2H⁺ + 2e^- -> H₂
OR
2H₂O + 2e^- -> H₂ + 2OH^-

Question 8

What happens when reacting with copper sulphate solution?

Answer 8

The sulphide ions aren’t easy to oxidise so oxygen is produced at the anode:
4OH^- -> 2H₂O + O₂ + 4e^-
OR
2H₂O -> O₂ + 4H⁺ + 4e^-

Question 9

What happens when reacting sulfuric acid?

Answer 9

Twice as much hydrogen in produced as oxygen. For every 4 moles of electrons, 1 mole of oxygen is produced and 2 moles of hydrogen. Actually, more than twice the amount of hydrogen is obtained for oxygen is more soluble in water. To obtain accurate results we carry out the reaction without collecting gas for a few minutes to saturate the water and then start to collect gas.

Question 10

How do you know if a half equation is reduction or oxidation?

Answer 10

Oxidation
Is
Loss (of electrons)
Reduction
Is
Gain (of electrons)