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

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

$$\begin{align*} Al_2O_3 \\ C_2H_5OH \\ CO_2 \\ Fe_2O_3 \\ H_2 \\ He \\ K^+ \\ Li^+ \\ N_2 \\ Na^+ \\ O^{2-} \\ \end{align*}$$

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) an element that is monoatomic
................................................................................................. [1]

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

(iii) an element that can be used as a fuel
................................................................................................. [1]

(iv) a gas that contributes to climate change
................................................................................................. [1]

(v) an ion that is formed when an atom gains electrons.
................................................................................................. [1]

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

[Table_1]

$$\begin{array}{|c|c|} \hline \text{type of particle} & \text{relative charge} \\ \hline \text{proton} & ext{.....................................................} \\ \text{neutron} & 0 \\ \text{electron} & ext{.....................................................} \\ \hline \end{array}$$

[2]

(c) Choose the two correct statements about nitrogen and hydrogen in a mixture. Tick (✓) two boxes.

- The nitrogen and hydrogen mixture can be separated by physical means.
- The nitrogen and hydrogen mixture is liquid at room temperature.
- The atoms of nitrogen and hydrogen in the mixture are chemically combined.
- Air is mainly a mixture of nitrogen and hydrogen.
- The bonding in both nitrogen and hydrogen molecules is covalent.

[2]

The table shows the masses of some ions in a 1000cm$^3$ sample of toothpaste.

[Table_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 sodium shown.
$$^{23}_{11}\text{Na}$$
number of electrons .....................................................................................................................
number of neutrons .....................................................................................................................
number of protons ........................................................................................................................ [3]

(b) Sodium reacts with chlorine to produce sodium chloride.
(i) State the colour of chlorine gas.
................................................................................................[1]

(ii) Chlorine is a diatomic molecule.
State the meaning of the term diatomic.
................................................................................................[1]

(iii) Complete the chemical equation for the reaction of sodium with chlorine.
$$2\text{Na} + \text{..........} \rightarrow ......\text{NaCl}$$ [2]

(iv) Sodium chloride is an ionic compound.
Describe two physical properties of ionic compounds.
1 ........................................................................................................................
2 ........................................................................................................................[2]

(c) The table shows some properties of four Group I elements.
[Table_1]
element | melting point /°C | boiling point /°C | atomic radius /nm
lithium | 181 | 1342 | 0.157
sodium | 98 | 883 | ...............
potassium | ............... | 760 | 0.235
rubidium | 39 | 686 | 0.250

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

(ii) Predict the physical state of rubidium at 700°C.
Give a reason for your answer.
................................................................................................[2]

(iii) Give two physical properties of Group I metals that are different from transition elements and state how they are different.
1 ........................................................................................................................
..........................................................................................................................
2 ..........................................................................................................................
.......................................................................................................................... [2]

(d) Aqueous chlorine reacts with aqueous sodium iodide.
$$\text{Cl}_2 + 2\text{NaI} \rightarrow 2\text{NaCl} + \text{I}_2$$
Explain how this equation shows that chlorine is more reactive than iodine.
................................................................................................[1]

This question is about acids and carbonates.

(a) Describe the colour change when excess acid is added to a solution of methyl orange in alkaline solution.   [2]

(b) Complete the word equation for the reaction of hydrochloric acid with calcium carbonate.  [2]

(c) Calcium carbonate decomposes when heated.

calcium carbonate $\rightarrow$ calcium oxide $+$ carbon dioxide

(i) Calcium carbonate is used in the manufacture of lime (calcium oxide).

State one other use of calcium carbonate.   [1]

(ii) The decomposition of calcium carbonate is endothermic.

State the meaning of the term endothermic.   [1]

(iii) The energy level diagram for the decomposition of calcium carbonate is shown.

Explain how the energy level diagram shows that this reaction is endothermic.   [1]

(iv) When 0.50 g of calcium carbonate decomposes, 120 cm$^3$ of carbon dioxide gas is produced.

Calculate the volume of carbon dioxide gas produced when 0.10 g of calcium carbonate is used.   [1]

(a) Name the changes of physical state when:

• oxygen gas is converted to liquid oxygen

• solid sulfur is converted directly to sulfur gas.

• the arrangement of the particles

• the motion of the particles.

1. State the meaning of the symbol \rightleftharpoons.

2. Give one use of sulfur dioxide other than in making sulfuric acid.

1. Choose the pH value which is acidic.
   Draw a circle around your chosen answer.
   pH 4 pH 7 pH 10 pH 14

2. Describe one effect of acid rain on buildings.

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

(i) State which compound, B, C, D or E, dissolves in water to form an acidic solution.   [1]

(ii) State which compound, B, C, D or E, is a saturated hydrocarbon.   [1]

(iii) State which compound, B, C, D or E, is an unreactive compound except in terms of burning.  [1]

(iv) State which compound, B, C, D or E, decolourises aqueous bromine.  [1]

(b) Ethanol can be manufactured from ethene and one other reactant.

Describe the manufacture of ethanol from ethene to include:  [4]

• the formula of ethene
• the name of the other reactant
• the conditions needed.

(c) Complete the table to show the name and uses of some petroleum fractions.   [3]

This question is about lithium and compounds of lithium.

(a) Lithium reacts with nitrogen to produce lithium nitride, $\text{Li}_3\text{N}$.

Complete the chemical equation for this reaction.  [2]

.....Li + $\text{N}_2 \rightarrow$ .....$\text{Li}_3\text{N}$

(b) Molten lithium bromide is electrolysed using carbon electrodes.

The apparatus is shown.

(i) Complete the diagram by labelling:   [2]

• the anode
• the electrolyte.

(ii) Name the products formed at each electrode. [2]

• positive electrode
• negative electrode

(iii) The carbon electrodes conduct electricity.

Give one other property that these electrodes must have.   [1]

(c) A compound of lithium has the formula $\text{C}_3\text{H}_5\text{O}_2\text{Li}_2$.  [2]

Complete the table to calculate the relative molecular mass of $\text{C}_3\text{H}_5\text{O}_2\text{Li}_2$.

A student investigates the rate of decomposition of aqueous hydrogen peroxide using 0.2 g of a catalyst. 

$$\text{2H}_2\text{O}_2 \rightarrow \text{2H}_2\text{O} + \text{O}_2$$

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

The results are shown on the graph.

(a) Deduce the time taken to collect 35 cm$^3$ of oxygen gas.   [1]

(b) The experiment is repeated using 0.2 g of smaller pieces of the catalyst.

All other conditions stay the same.

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

(c) Describe the effect each of the following has on the rate of decomposition of hydrogen peroxide.

All other conditions stay the same. [2]

• The reaction is carried out at a higher temperature.
• The reaction is carried out using a lower concentration of hydrogen peroxide. 

(d) Hydrogen peroxide reduces sodium chlorate(I), NaClO, to sodium chloride.

$$\text{H}_2\text{O}_2 + \text{NaClO} \rightarrow \text{NaCl} + \text{H}_2\text{O} + \text{O}_2$$

Describe how this equation shows that sodium chlorate(I) has been reduced.   [1]