4 Chemical Changes - Electrolysis

Question 1

What is electrolysis?

Answer 1

Using electricity to break down a substance

Question 2

What happens to an ionic substance when it is melted or dissolved in water?

Answer 2

The ions become free to move around

Question 3

What is the name for the positive electrode?

Answer 3

The anode

Question 4

What is the name for the negative anode?

Answer 4

The cathode

Question 5

Do positive ions move to the anode or the cathode?

Answer 5

Cathode

Question 6

Do negative ions move to the anode or the cathode?

Answer 6

Anode

Question 7

At which electrode would Zn2+(aq) turn into Zn(s)?

Answer 7

Cathode (needs to gain electrons)

Question 8

At which electrode would Cl-(aq) turn into Cl2(g)?

Answer 8

Anode (needs to lose electrons)

Question 9

Balance the equation: Al3+ + e- gives Al

Answer 9

Al3+ + 3e- –> Al

Question 10

Balance the equation: Cl- gives Cl2 + e-

Answer 10

2Cl- –> Cl2 + 2e-

Question 11

Balance the equation: O2- gives O2 + e-

Answer 11

2O2- –> O2 + 4e-

Question 12

What will be the products for the electrolysis of molten iron bromide?

Answer 12

Iron and bromine

Question 13

What will be the products for the electrolysis of molten zinc oxide?

Answer 13

Zinc and oxygen

Question 14

When is electrolysis used to extract metals from their ores?

Answer 14

When the metals are more reactive than carbon, e.g. aluminium

Question 15

What are the two main disadvantages of using electrolysis to extract metals?

Answer 15

Requires a large amount of energy to melt the compounds and to produce the necessary electricity

Question 16

Why is aluminium oxide mixed with cryolite when extracting aluminium?

Answer 16

To lower the melting point from 0ver 2000 degrees celsius down to 900 degrees celsius

Question 17

What is produced at the anode and cathode in the electrolysis of aluminium oxide?

Answer 17

Aluminium at the cathode and oxygen at the anode

Question 18

Why does the anode need to be replaced in the electrolysis of aluminium oxide?

Answer 18

The carbon anode is non-inert (reactive). The oxygen reacts with the is to produce carbon dioxide.

Question 19

In the electrolysis of sodium chloride solution, what are the products?

Answer 19

Chlorine gas and hydrogen gas

Question 20

Why is sodium not produced in the electrolysis of sodium chloride solution?

Answer 20

It is more reactive than hydrogen so hydrogen is produced instead.

Question 21

What is produced at the anode in electrolysis of solutions?

Answer 21

Either a halogen or oxygen (when there is no halogen present)