Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2022 Summer Zone 2

(a) A list of symbols and formulae is shown.

Br^-
CH₄
CO₂
Cu²⁺
H₂
K⁺
Na⁺
N₂
O₂
U
Answer the following questions using these symbols or formulae.
Each symbol or formula may be used once, more than once or not at all.

State which symbol or formula represents:

(i) a compound that is a product of respiration
............................................................................................................. [1]

(ii) an ion that gives a lilac colour in a flame test
............................................................................................................. [1]

(iii) a gas which is 21% of clean, dry air
............................................................................................................. [1]

(iv) an element that has a radioactive isotope used as a source of energy
............................................................................................................. [1]

(v) an ion formed when an atom gains an electron.
............................................................................................................. [1]

(b) Complete the table to show the relative masses of a proton, a neutron and an electron.

[Image_1: Table with headers 'type of particle' and 'relative mass'.
Rows: proton - 1, neutron - , electron - ] [2]

(c) Choose the two correct statements about carbon dioxide.
Tick (✓) two boxes.

Carbon dioxide is a mixture of two elements.
Carbon dioxide is an acidic oxide.
Carbon dioxide has ionic bonding.
Carbon dioxide has a giant covalent structure.
There are three atoms in a molecule of carbon dioxide.
[2]

The table shows the masses of some ions in a 1000 cm³ sample of toothpaste.

[Table_1]

(a) Answer these questions using only the information in the table.

(i) State which positive ion has the lowest mass in 1000 cm³ of toothpaste.
.................................................................................................................. [1]

(ii) Name the compound that contains Mg²⁺ and SO₄^2- ions.
.................................................................................................................. [1]

(iii) Calculate the mass of sodium ions in 200 cm³ of toothpaste.

mass = ............................... g [1]

(b) Describe a test for chloride ions.
test ...........................................................................................................
observations .............................................................................................. [2]

(c) Toothpaste also contains glycerol.
The structure of glycerol is shown.



Deduce the formula of glycerol to show the number of atoms of carbon, hydrogen and oxygen.
.................................................................................................................. [1]

(d) Glycerol is an alcohol. Ethanol is also an alcohol.

(i) Draw the structure of ethanol to show all of the atoms and all of the bonds.

[1]

(ii) Name the two products formed when ethanol undergoes complete combustion.
................................................................ and ............................................................... [2]

(iii) Give one use of ethanol.
.................................................................................................................. [1]

This question is about Group I and Group VII elements.

(a) Deduce the number of electrons, neutrons and protons in one atom of the isotope of potassium shown.$$^{40}_{19}K$$

number of electrons \text{.............................................................}
number of neutrons \text{.............................................................}
number of protons \text{.............................................................}[3]

(b) Complete the chemical equation for the reaction of potassium with water to form potassium hydroxide and a gas which pops with a lighted splint.

$$2K + \ldots\text{ H}_2\text{O} \rightarrow 2\text{KOH} + \ldots$$ [2]

(c) The table shows some properties of four Group I elements.

[Table_1: element, melting point /°C, boiling point /°C, relative hardness; lithium, 181, 1342, 5.0; sodium, \text{................}, 883, 0.7; potassium, 63, 760, \text{................}; rubidium, 39, 686, 0.2]

(i) Complete the table by predicting:
• the melting point of sodium
• the relative hardness of potassium.[2]

(ii) Predict the physical state of potassium at 100°C. Give a reason for your answer.\text{.............................................................}
\text{.............................................................} [2]

(d) Aqueous bromine reacts with aqueous potassium iodide.$$\text{Br}_2 + 2\text{KI} \rightarrow 2\text{KBr} + \text{I}_2$$
(i) Explain how this equation shows that bromine is more reactive than iodine.\text{.............................................................}
\text{.............................................................} [1]

(ii) State the colour of aqueous iodine.\text{.............................................................} [1]

(e) Bromine is a diatomic molecule.
State the meaning of the term diatomic.\text{.............................................................} [1]

(f) Bromine liquid turns into a gas very easily at room temperature. Choose the word which best describes a substance that evaporates easily. Draw a circle around your chosen answer.

\underline{\text{conductor \ flammable \ malleable \ volatile}} [1]

This question is about acids and bases.
(a) Name the type of chemical reaction which occurs when an acid reacts with a base.
.............................................................................................................................. [1]
(b) Describe the colour of litmus in acidic and alkaline solutions.
in acidic solution ...........................................................................................................................
in alkaline solution ......................................................................................................................... [2]
(c) Complete the word equation for the reaction of nitric acid with calcium hydroxide.

[2]
(d) When nitric acid reacts with calcium hydroxide, the temperature of the reaction mixture increases.
(i) Choose the word which best describes this reaction.
Draw a circle around your chosen answer.
decomposition endothermic exothermic oxidation [1]
(ii) Complete the energy level diagram for the reaction of nitric acid with calcium hydroxide by writing the words:
• reactants
• products.
[1]
(e) Calcium hydroxide is slaked lime.
Give one use of slaked lime.
............................................................................................................................. [1]

(a) The changes of state of aluminium are shown.
[Image_1: Diagram showing 'solid aluminium' to 'liquid aluminium' labeled A and 'liquid aluminium' to 'aluminium gas' labeled B]
Name the changes of state represented by A and B.
A ......................................................
B ......................................................

(b) Use the kinetic particle model to describe the differences between solid aluminium and liquid aluminium in terms of:
- the arrangement of the particles ......................................................
............................................................................................................
- the separation of the particles. ....................................................
............................................................................................................

(c) Aluminium ore contains aluminium oxide.
(i) Name the main ore of aluminium.
............................................................................................................
(ii) Aluminium is extracted from aluminium oxide by electrolysis.
Explain why aluminium is extracted by electrolysis and not by reduction with carbon.
............................................................................................................

(d) Aluminium can be used to reduce iron(III) oxide to iron.
$$ \text{Fe}_2\text{O}_3 + 2\text{Al} \rightarrow 2\text{Fe} + \text{Al}_2\text{O}_3 $$
Describe how this equation shows that iron(III) oxide is reduced.
............................................................................................................

(e) Aluminium is used for electric cables.
State one other use of aluminium.
Give a reason for this use in terms of the properties of aluminium.
use of aluminium ......................................................
reason for this use ......................................................

(f) Deduce the electronic structure of aluminium.
Use the Periodic Table to help you.
............................................................................................................

(a) The structures of four organic compounds, C, D, E and F, are shown.

(i) State which two of the compounds, C, D, E and F, are in the same homologous series.
.................................... and ................................................ [1]
(ii) State which compound, C, D, E or F, is the monomer used to make poly(ethene).
.................................................................................................... [1]
(iii) State which compound, C, D, E or F, is a carboxylic acid.
..................................................................................................... [1]

(b) Petroleum is a mixture of hydrocarbons, which can be separated into fractions.
Describe how petroleum is separated into fractions to include:

• the name of the process used to separate the fractions
• how this process separates the different fractions.

This question is about sodium and compounds of sodium.
(a) Sodium is a metal in Group I of the Periodic Table.
(i) Give two physical properties of all metals.
1 ..................................................................................................................
2 ..................................................................................................................
[2]
(ii) Give one physical property of Group I metals that is different from most other metals and state how it is different.
.......................................................................................................................
.......................................................................................................................
[1]
(b) Sodium reacts with oxygen to form sodium oxide, $Na_2O$.
Complete the chemical equation for this reaction.
.....Na + O$_2$ → .....Na$_2$O
[2]
(c) The diagram shows the apparatus used to electrolyse molten sodium iodide.

(i) Complete the diagram by labelling:
• the electrolyte
• the cathode.
[2]
(ii) Name the products formed at each electrode.
positive electrode .................................................................................................
negative electrode .................................................................................................
[2]
(d) A compound of sodium has the formula $Na_2S_2O_3$.
Complete the table to calculate the relative molecular mass of $Na_2S_2O_3$.
[Table_1]
relative molecular mass = .........................
[2]

A student investigates the reaction of small pieces of calcium carbonate with dilute hydrochloric acid.
The hydrochloric acid is in excess.

$$CaCO_3 + 2HCl \rightarrow CaCl_2 + CO_2 + H_2O$$

The rate of reaction is found by measuring the volume of carbon dioxide gas produced as time increases.

The results are shown on the graph.



(a) Deduce the volume of carbon dioxide gas at 35 s.

volume = ............................ cm³ [1]

(b) The experiment is repeated at a higher temperature.

All other conditions stay the same.

Draw a line on the grid to show how the volume of carbon dioxide gas produced changes as time increases. [2]

(c) Describe the effect each of the following has on the rate of reaction of calcium carbonate with dilute hydrochloric acid.

All other conditions stay the same.

• The reaction is carried out using a higher concentration of hydrochloric acid.
.........................................................................................................................................................................

• The reaction is carried out using powdered calcium carbonate.
......................................................................................................................................................................... [2]

(d) When 0.11 g of calcium carbonate is used, 25 cm³ of carbon dioxide gas is produced.

Calculate the mass of calcium carbonate needed to produce 100 cm³ of carbon dioxide gas.

mass of calcium carbonate = ............................ g [1]

(e) State one use of calcium carbonate.
......................................................................................................................................................................... [1]