Past Paper Mistakes

Question 1

Why is diamond hard?

Answer 1

Each carbon atom forms four strong covalent bonds.

Giant covalent structure.

The strong covalent bonds require a significant amount of energy to break, making diamond very hard.

Question 2

Why is graphite soft?

Answer 2

Each carbon atom forms three covalent bonds, creating layers of hexagonal rings.

The layers are held together by weak intermolecular forces, allowing them to slide over one another.

This structure results in as soft and slippery material.

Question 3

What is a use of fullerene?

Answer 3

drug delivery (round the body)
* hydrogen storage
* anti-oxidants
* reduction of bacterial growth
* catalysts

Question 4

Why does propanone have a low boiling point?

Answer 4

Weak intermolecular forces which require little energy to overcome.

Question 5

Explain why the reactivity of elements changes going down Group 1.

Answer 5

reactivity increases (going down
the group)

(because) the outer electron /
shell is further from the nucleus

(so) there is less attraction
between the nucleus and the
outer electron / shell

(so) the atom loses an electron
more easily

Question 6

Explain why sodium oxide has a high melting point.

Answer 6

giant structure
(with) strong (electrostatic)
forces of attraction between
(oppositely charged) ions

(so) large amounts of energy
are needed to break the bonds /
forces

Question 7

Write an ionic equation for the neutralisation of hydrochloric acid with
potassium hydroxide.

Answer 7

H+ + OH− → H2O

Question 8

Soluble salts can be produced by reacting dilute hydrochloric acid with an
insoluble solid.

Copper, copper carbonate and copper oxide are insoluble solids.

Which of these insoluble solids can be used to make a copper salt by reacting the
solid with dilute hydrochloric acid?

Answer 8

copper carbonate and copper oxide

Question 9

Explain why alloys are harder than pure metals.

Answer 9

in an alloy) the atoms are of
different sizes

(so) the layers (of atoms in an
alloy) are distorted

(so in an alloy) the layers slide
over each other less easily (than
in a pure metal)

Question 10

Electrolysis and chemical cells both involve chemical reactions and electricity.

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

Answer 10

electrolysis uses electricity to
produce a chemical reaction

(but) cells use a chemical
reaction to produce electricity

Question 11

Some of the copper produced did not stick to the negative electrode but fell to the
bottom of the beaker.

Suggest how the students could find the total mass of copper produced.

Answer 11

filter the mixture

wash and dry the copper /
residue

weigh the copper collected

add to the increase in mass of
the electrode