Electrolysis

Question 1

What is electrolysis?

Answer 1

Using electricity to break down an ionic compound into elements

Question 2

Why must ionic compounds be liquid or dissolved in water for electrolysis to work?

Answer 2

So ions can move and carry charge

Question 3

Explain what happens at the cathode (negative electrode)

Answer 3

Positive ions (cations) are attracted and gain electrons in reduction

Question 4

Explain what happens at the anode (positive electrode)

Answer 4

Negative ions (anions) are attracted and lose electrons in oxidation

Question 5

At which electrode would Zn2+ turn into Zn?

Answer 5

Negative electrode

Question 6

At which electrode would Cl- turn into Cl2?

Answer 6

Positive electrode

Question 7

Complete the half equation: Al3+ + ___ —> ___

Answer 7

Al3+ + 3e- —> Al

Question 8

Complete the half equation: Cl- —> ___ + ___

Answer 8

2Cl- —> Cl2 + 2e-

Question 9

Complete the half equation: ___O2- —> ___ + ___

Answer 9

2O2- —> O2 + 4e-

Question 10

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

Answer 10

Iron and bromine

Question 11

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

Answer 11

Zinc and oxygen

Question 12

What is the disadvantages of using electrolysis?

Answer 12

Requires a large amount of electrical energy which is expensive

Question 13

Why is aluminium oxide mixed with cryolite when extracting aluminium?

Answer 13

To lower the melting point

Question 14

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

Answer 14

Aluminium at the cathode and oxygen at the anode

Question 15

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

Answer 15

The oxygen reacts with the carbon electrode to produe carbon dioxide

Question 16

Where does hydrogen come from in electrolysis of solutions?

Answer 16

Water

Question 17

Where does oxygen come from in electrolysis of solutions?

Answer 17

Hydroxide ions from water

Question 18

When is hydrogen made at the negative electrode in solutions?

Answer 18

If the metal is more reactive than hydrogen

Question 19

When is oxygen made at the positive electrode in solutions?

Answer 19

If the non-metal ion is not a halide

Question 20

Which two ions are involved in electrolysis when water is present?

Answer 20

H+ ions and OH- ions

Question 21

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

Answer 21

Chlorine gas, hydrogen gas and sodium hydroxide

Question 22

In the electrolysis of sodium chloride solution, why is hydrogen gas produced?

Answer 22

Sodium is more reactive than hydrogen

Question 23

In the electrolysis of sodium chloride solution, why is chlorine gas produced?

Answer 23

Chloride is a halide ion

Question 24

In the electrolysis of sodium chloride solution, why is sodium hydroxide produced?

Answer 24

Left over sodium ions and hydroxide ions remain in the water

Question 25

What is the half equation for the formation of hydrogen gas at the negative electrode?

Answer 25

2H+ + 2e- —> H2

Question 26

What is the half equation for the formation of oxygen gas at the positive electrode?

Answer 26

4OH- —> O2 + H2O + 4e-

Question 27

On an electrolysis diagram, what are the things that need to be labelled?

Answer 27

Power supply, positive electrode, negative electrode, electrolyte or metal solution

Question 28

If students are testing different metal solutions to see what is formed, what is the independent variable?

Answer 28

The type of metal solution