Questions Corrections 2021

Question 1

Give two reasons why the discovery of gallium helped Mendeleev’s periodic table to become accepted

Answer 1

Fitted in a gap
Properties were predicted correctly

Question 2

Which insoluble solid can be used to make a copper salt by reacting the solid with dilute HCL

Answer 2

Copper carbonate and copper oxide only

Question 3

Why is the mixture filtered in the method for magnesium sulfate crystals

Answer 3

To remove excess magnesium oxide

Question 4

Why are alloys harder than pure metals

Answer 4

The atoms are of different sizes
So the layers are distorted
So the layers slide over each other less easily

Question 5

Explain the difference between the processes in electrolysis and in a chemical cell

Answer 5

Electrolysis uses electricity to produce a chemical reaction
Cells use a chemical reaction to produce electricity

Question 6

Some of the copper produced did not stick to the negative electrode but fell to the bottom of the beaker
Suggest how students could find the total mass is copper produced

Answer 6

Filter the mixture
Wash and dry the copper
Weigh the copper collected
Add to the increase in mass of the electrode