Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2021 Winter Zone 3

(a) A list of formulae is shown.
Br_2
CO
CO_2
CH_4
C_2H_6
HCl
KBr
LiCl
MgCl_2
O_2
SO_2
Answer the following questions using these formulae.
Each formula may be used once, more than once or not at all.
State which formula represents:
(i) a compound that gives a red colour in a flame test
...................................................................................................................................................
[1]
(ii) a compound containing an ion with a 2+ charge
...................................................................................................................................................
[1]
(iii) a compound that is a product of respiration
...................................................................................................................................................
[1]
(iv) a compound used as a food preservative
...................................................................................................................................................
[1]
(v) an element that is used in the production of steel.
...................................................................................................................................................
[1]
(b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of hydrogen chloride. Show outer shell electrons only.

[2]
(c) State whether carbon dioxide is a basic oxide or an acidic oxide.
Give a reason for your answer.
...................................................................................................................................................
.....................................................................................................................
[1]

The table shows the masses of some of the ions in 1000 cm^3 of water from a river.

[Table_1]

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

(i) State which positive ion has the lowest concentration.
.............................................................................................................................................. [1]

(ii) Name the compound containing $\text{Ca}^{2+}$ and $\text{NO}_3^-$ ions.
.............................................................................................................................................. [1]

(iii) Calculate the mass of sulfate ions in 500 cm^3 of river water.
mass = ............................... mg [1]

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

(c) Compound A is found in river water.
The structure of compound A is shown.



(i) On the structure draw a circle around the alcohol functional group. [1]

(ii) Deduce the formula of compound A to show the number of carbon, hydrogen, oxygen and nitrogen atoms.
.............................................................................................................................................. [1]

(iii) Another compound found in river water has the formula $\text{C}_4\text{H}_8\text{O}_2$.
Complete the table to calculate the relative molecular mass of this compound.

[Table_2]

relative molecular mass = ............................... [2]

Iron is extracted in a blast furnace using a mixture of iron ore, coke (carbon), air and calcium carbonate (limestone).
(a) Give two reasons why air is blown into the blast furnace.
1 .....................................................................................................................................
2 .....................................................................................................................................
[2]
(b) Magnetite is an ore of iron which contains a compound of iron with the formula $\text{Fe}_3\text{O}_4$.
(i) Give the name of another ore of iron.
.................................................................................................................................
[1]
(ii) In the blast furnace $\text{Fe}_3\text{O}_4$ is reduced to Fe.
Complete the chemical equation for the reduction of $\text{Fe}_3\text{O}_4$.
$\text{Fe}_3\text{O}_4 + 4\text{CO} \rightarrow .....\text{Fe} + .....\text{CO}_2$
[2]
(iii) Explain how this equation shows that $\text{Fe}_3\text{O}_4$ is reduced.
.........................................................................................................................................
[1]
(c) Calcium carbonate (limestone) is added to the blast furnace.
The calcium carbonate undergoes thermal decomposition.
Give the meaning of the term thermal decomposition.
....................................................................................................................................
[2]
(d) Iron can form alloys such as vanadium steel.
(i) State the meaning of the term alloy.
......................................................................................................................................
...........................................................................................................................................
[1]
(ii) Choose from the diagrams, B, C, D or E, the structure which best represents an alloy.

structure ..................................
[1]
(iii) The symbol for an isotope of vanadium is shown.
$^{51}_{23}\text{V}$
Deduce the number of electrons, neutrons and protons in one atom of this isotope of vanadium.
number of electrons ...........................................................................................
number of neutrons .........................................................................................
number of protons ..........................................................................................
[3]
(iv) Vanadium is malleable and conducts electricity.
Give two other physical properties of vanadium that are characteristic of all metals.
1 ..................................................................................................................................
2 ..................................................................................................................................
[2]

The table shows some properties of four halogens in Group VII.

[Table_1]

(a) (i) Complete the table by predicting:
● the boiling point of iodine
● the density of bromine.
[2]

(ii) Describe the trend in the melting points of the halogens down Group VII.
...............................................................................................................................................................................
[1]

(b) (i) Deduce the electronic structure of chlorine. Use the Periodic Table to help you.
...............................................................................................................................................................................
[1]

(ii) Explain why a bromide ion has a single negative charge.
...............................................................................................................................................................................
[1]

(c) Scientists have predicted that sodium astatide reacts with chlorine.
Complete the word equation for this reaction.


[2]

(d) Hydrogen chloride is produced when chlorine reacts with ammonia. An aqueous solution of hydrogen chloride is acidic.
Describe how you could determine the pH of an acidic solution without using a pH meter.
...............................................................................................................................................................................
...............................................................................................................................................................................
[2]

The table shows the structures of some organic compounds.

(a) Complete the table by naming the homologous series.

The first one has been done for you. [2]

(b) Draw the structure of a compound containing two carbon atoms which belongs to the same homologous series as compound F.

Show all of the atoms and all of the bonds. [1]

(c) Compound G reacts with bromine.

Choose from the structures, P, Q, R or S, the structure of the product formed.  [1]

(d) (i) Compound G can be obtained by cracking petroleum fractions.

Describe what is meant by the term cracking.   [2]

(ii) Name the product of the reaction when compound G reacts with steam.  [1]

(iii) Many molecules of compound G can join together to form a compound with a very long chain.

Choose from the list the general name given to a compound that is formed by the addition of many small units.

Draw a circle around the correct answer.  [1]

isomer      monomer      naphtha       polymer 

(e) State the names of the two compounds formed during the complete combustion of compound H.
........................................ and ................................................. [2]

The diagram shows part of the structures of sodium chloride and pentane at room temperature and pressure.
[Diagram of NaCl and pentane structures]
(a) Describe the differences in the physical properties of these substances in terms of:
• volatility
sodium chloride ..................................................................................................................
pentane ..........................................................................................................................
• solubility in water
sodium chloride ..................................................................................................................
pentane ..........................................................................................................................
• electrical conductivity when molten (liquid).
sodium chloride ..................................................................................................................
pentane ..........................................................................................................................

(b) Concentrated aqueous sodium chloride is electrolysed using carbon (graphite) electrodes.
Name the gas produced at the positive electrode.
..........................................................................................................................

(c) Pentane is a fuel. Under some conditions pentane forms carbon monoxide.
(i) State the condition under which pentane forms carbon monoxide.
.......................................................................................................................... [1]
(ii) State one adverse effect of carbon monoxide on health.
..........................................................................................................................

This question is about aluminium and the extraction of metals.
(a) When aluminium is heated above 660°C it changes from solid to liquid.
(i) Name the change of state from solid to liquid.
..................................................................................................................................................... [1]
(ii) Use the kinetic particle theory to describe the differences between solid aluminium and liquid aluminium in terms of:
• the separation of the particles
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.........................................................................................................................................................
.........................................................................................................................................................
• the motion of the particles.
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......................................................................................................................................................... [4]
(b) Aluminium is extracted from aluminium ore by electrolysis.
Explain why aluminium is extracted by electrolysis and \textit{not} by reduction with carbon.
....................................................................................................................................................... [1]
(c) Give \textit{two} reasons why aluminium is used in the manufacture of aircraft.
1 ..................................................................................................................................................
2 .................................................................................................................................................. [2]
(d) Give \textit{one} advantage of recycling aluminium.
......................................................................................................................................................... [1]
(e) The table compares the ease of reduction of four metal oxides when heated with carbon.

[Table_1]

A student investigated the reaction of small pieces of zinc with dilute hydrochloric acid. The hydrochloric acid was in excess.

Zn + 2HCl → ZnCl₂ + H₂

The rate of reaction is found by measuring the increase in volume of hydrogen gas with time.

The results are shown on the graph.



(a) Deduce the time taken from the beginning of the experiment to collect 30cm³ of hydrogen gas.
time = .......................... s [1]

(b) The experiment was repeated using dilute hydrochloric acid of a higher concentration.
All other conditions stayed the same.
Draw a line on the grid to show how the volume of hydrogen gas changes with time. [2]

(c) Describe the effect each of the following has on the rate of reaction of zinc with dilute hydrochloric acid.
All other conditions stay the same.

• The reaction is carried out at a lower temperature.
.......................................................................

• The reaction is carried out using zinc powder instead of small pieces of zinc.
...................................................................... [2]

(d) When 0.065g of zinc is used, 24cm³ of hydrogen gas is formed.
Calculate the mass of zinc needed to produce 96cm³ of hydrogen gas.
mass of zinc = .......................... g [1]

(e) Aqueous ammonia is added to aqueous zinc chloride.
Describe the observations when a few drops of aqueous ammonia are added and when excess aqueous ammonia is added.
a few drops of aqueous ammonia ..............................................................
excess aqueous ammonia ............................................................. [2]