Past Paper Mistakes (Paper 1)

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

Question 12

Why can copper not react with sulfuric acid in the crystallizing salts practical?

Answer 12

Will not displace hydrogen as copper is too low on reactivity series.

Question 13

Why can sodium not react with sulfuric acid in the crystallizing salts practical?

Answer 13

Could explode

Question 14

One similarity between sodium (11) and potassium’s (19) electronic structure?

Answer 14

Both have one outer shell electron.

Question 15

Explain the results in figure 3.

Answer 15

the temperature rises because
the reaction is exothermic

until 0.8 g (zinc) is added

(so) there is no additional
reaction

(because) zinc is in excess

Question 16

Explain why using a polystyrene cup gives more accurate results than using a
glass beaker for an exothermic reaction.

Answer 16

polystyrene is a better (thermal)
insulator

(so) there is less energy transfer
to the surroundings

Question 17

Calcium (group 2) and chlorine (group 7) react to produce calcium chloride.

Describe what happens to calcium atoms and chlorine atoms when the ionic
compound calcium chloride is formed.

Answer 17

each calcium atom loses two
electrons

(and) each chlorine atom gains
one electron

(so) one calcium atom reacts
with two chlorine atoms

(to form) Ca2+ ions and Cl- ions

Group 2 have a 2+ charge and Group 7 have a -1 charge after they have formed compound. This question is asking what happens to get to that stage.

Question 18

What factors determine the ions discharged during the electrolysis of an aqueous solution using inert electrodes?

Answer 18

The relative reactivity of the elements involved

Question 19

What is produced at the cathode if the metal is more reactive than hydrogen?

Answer 19

Hydrogen

Question 20

What is produced at the anode unless halide ions are present in the solution?

Answer 20

Oxygen

Question 21

What is produced at the anode if the solution contains halide ions?

Answer 21

Halogen

Question 22

What do water molecules break down into during electrolysis?

Answer 22

Hydrogen ions and hydroxide ions

Question 23

Fill in the blank: At the _______ electrode, hydrogen is produced if the metal is more reactive than hydrogen.

Answer 23

cathode

Question 24

True or False: Oxygen is produced at the anode when halide ions are present.

Answer 24

False

Question 25

How does a hydrogen fuel cell produce a potential difference?

Answer 25

hydrogen is oxidised (electrochemically) to produce water

Question 26

Describe how iron conducts thermal energy.

Answer 26

thermal energy is transferred by delocalised electrons

Question 27

Explain why mixing iron with other metals makes alloys which are harder than pure iron.

Answer 27

(the alloy / mixture has) different sized atoms (so the) layers are distorted (so the) layers cannot easily slide

Question 28

Why does propane have a low boiling point?

Answer 28

propane is a small molecule the intermolecular forces are weak which require little energy to overcome

Question 29

Explain what happens to the pH of an acid as the acid is diluted with water.

Answer 29

pH increases (because) the concentration of hydrogen ions decreases

Question 30

Methane is a gas at room temperature but poly(ethene) is a solid at room temperature. Explain why methane and poly(ethene) exist in different states at room temperature.

Answer 30

methane has (much) smaller molecules (so) has weaker intermolecular forces (so the intermolecular forces) need less energy to overcome (so) the boiling / melting point is lower (and methane is a gas)

Question 31

Argon has the atomic number 18 Explain why argon does not form compounds.

Answer 31

(atoms of) argon have a stable arrangement of electrons (so) argon (atoms) do not share / transfer electrons

Question 32

Tellurium is the element with atomic number 52 Predict whether tellurium reacts with metals. Explain your answer. Answer in terms of the position of tellurium in the periodic table

Answer 32

yes, because tellurium is towards the right of the periodic table (so) tellurium is a non-metal

Question 33

Explain why the pH of an acid depends on: * the strength of the acid * the concentration of the acid.

Answer 33

Strength of the acid: Strong acids fully ionize )in water, releasing more hydrogen ions (H⁺), resulting in a lower pH. Weak acids only partially ionize, releasing fewer H⁺ ions, so they have a higher pH. Concentration of the acid: A higher concentration means more acid molecules in solution, producing more H⁺ ions and lowering the pH. A lower concentration produces fewer H⁺ ions, so the pH is higher.