C6 - Electrolysis Flashcards Preview

Chemistry - 2 Chemical Reactions and Energy Changes > C6 - Electrolysis > Flashcards

Flashcards in C6 - Electrolysis Deck (13):
1

What is electrolysis?

The breakdown of a substance using electricity.

2

How are ionic compounds electrolysed?

When they are molten or dissolved in water because their ions are then free to move and carry their charge to the electrodes.

3

What happens during the process of electrolysis?

- Positive ions move to the cathode (negative electrode).
- Negative ions move to the anode (positive electrode).

4

What happens at the cathode (N) during electrolysis?

Positive ions gain electrons, so they are reduced.

5

What happens at the anode (P) during electrolysis?

Negative electrons lose their extra electrons so they are oxidised.

6

What happens when electrolysis occurs in aqueous solution?

- The less reactive element, either hydrogen or the metal is usually produced at the cathode.
- At the anode, oxygen gas is given off from discharged hydroxide ions produced from water or a halogen produced if thee electrolyte is a solution of a halide.

7

What is electrolysed in the extraction of aluminium metal?

Aluminium oxide from the ore bauxite.

8

Why is aluminium oxide mixed with molten cryolite?

- To lower its melting point reducing the energy needed to extract the aluminium.

9

What happens in electrolysis during the extraction of aluminium?

- Aluminium forms at the cathode.
- Oxygen forms at the anode.

10

Why are carbon anodes replaced regularly?

- They gradually burn away as the oxygen reacts with the hot carbon anodes, forming carbon dioxide gas.

11

What happens when you electrolyse sodium chloride solution?

3 products, chlorine gas and hydrogen gas given off at the electrodes, plus sodium hydroxide solution left in the solution.

12

Where is hydrogen produced in aqueous solution?

- At the cathode as H+(aq) ions are discharged from solution in preference to Na+(aq) ions.

13

Where is chlorine produced in aqueous solution?

At the anode as Cl-(aq) ions are discharged from solution in preference to OH-(aq) ions.