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

(a) The electronic structures of five atoms, A, B, C, D and E, are shown.

Answer the following questions about these electronic structures.
Each electronic structure may be used once, more than once or not at all.

State which electronic structure, A, B, C, D or E, represents:

(i) an atom of an element in Group VI of the Periodic Table
......................................................................................................................... [1]

(ii) an atom of a reactive metal
......................................................................................................................... [1]

(iii) an atom with a proton number of 17
......................................................................................................................... [1]

(iv) an atom that forms a stable ion with a charge of 2–
......................................................................................................................... [1]

(v) an atom of oxygen.
......................................................................................................................... [1]

(b) Complete the table to show the number of electrons, neutrons and protons in the bromine atom and fluoride ion shown.

[Table_1 showing \( \begin{array}{|c|c|c|c|} \hline & \text{number of electrons} & \text{number of neutrons} & \text{number of protons} \\ \hline ^{81}_{35}\text{Br} & 35 & & \\ \hline ^{19}_{9}\text{F}^- & & 10 & \\ \hline \end{array} \)] [3]

[Total: 8]

The table shows the masses of some of the ions in 1000 $cm^3$ of fruit juice.

[Table with descriptions of masses of ions]
(a) Answer these questions using only the information in the table.
(i) State which negative ion has the highest mass in 1000 $cm^3$ of fruit juice. ............................................................................................................................... [1]
(ii) Give the formulae of the ions in sodium nitrate.
.................................................. and .................................................. [1]
(iii) Calculate the mass of ammonium ions in 250 $cm^3$ of fruit juice.
mass = ................................. $mg$ [1]

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

(c) Phosphate ions, $PO_4^{3-}$, are present in most fertilisers. Phosphate ions contain phosphorus.
(i) State the names of two other elements that are in most fertilisers.
1 .................................................................................................................................
2 ................................................................................................................................. [2]
(ii) Explain why farmers put fertilisers on fields where crops are to be grown.
.................................................................................................................................
................................................................................................................................. [1]

(d) A student heated ammonium sulfate with sodium hydroxide in a test-tube.
(i) Complete the equation for this reaction.
$$(NH_4)_2SO_4$ + .....$NaOH →$ .....$NH_3$ + $Na_2SO_4$ + $2H_2O$$ [2]
(ii) Concentrated aqueous ammonia releases fumes of ammonia gas.
A long glass tube is set up as shown.
[Image of experimental setup]
At first, the red litmus paper does not turn blue. After a short time, the litmus paper turns blue.
Explain these observations using the kinetic particle model.
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
................................................................................................................................. [3]

The table shows some properties of five halogens.

[Table_1]

(a) (i) Complete the table by predicting:
• the melting point of chlorine
• the density of liquid fluorine at its boiling point
• the colour of astatine. [3]

(ii) Deduce the state of bromine at 0°C. Explain your answer. [2]

(b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of chlorine. Show the outer shell electrons only.

[2]

(c) (i) Astatine is a radioactive element. An isotope of astatine, $^{217}_{85}\text{At}$, decays to form an isotope of bismuth, $^{213}_{83}\text{Bi}$. Describe what happens to the number of nucleons during this decay. [1]

(ii) One of these statements about isotopes is incorrect. Tick the box with the incorrect statement.
The isotope $^{235}\text{U}$ is a source of energy.
Some radioactive isotopes can be used to treat cancer.
All isotopes are radioactive.
Isotopes of the same element have the same number of protons. [1]

(a) The structure of two organic compounds, F and G, are shown.

(i) Compound F is an unsaturated compound.
Describe a chemical test for an unsaturated compound.
test ................................................................. .................................................................
observations ................................................................. .........................................................
[2]
(ii) Compound F is reduced to compound G using hydrogen and a catalyst.
State what is meant by the term catalyst.
................................................................. .................................................................
................................................................. .................................................................
[1]
(iii) Compound G is a saturated hydrocarbon.
Name the saturated hydrocarbon which contains two carbon atoms.
................................................................. .................................................................
[1]
(b) Compound G is oxidised by nitric acid to compound H.
The structure of compound H is shown.

(i) Deduce the formula of compound H to show the number of carbon, hydrogen and oxygen atoms.
................................................................. .................................................................
[1]
(ii) Compound H contains two carboxylic acid functional groups.
Ethanoic acid also contains a carboxylic acid functional group.
Draw the structure of ethanoic acid. Show all of the atoms and all of the bonds.
[1]
(iii) Describe the observations made when ethanoic acid reacts with:
universal indicator solution ................................................................. ............................
sodium. ................................................................. .................................................................
[2]
(c) A student’s graph of how the pH changes when aqueous ammonia is added slowly to dilute ethanoic acid is shown.

(i) Deduce the pH of the dilute ethanoic acid before the addition of aqueous ammonia.
pH = .................................................................
[1]
(ii) Deduce the volume of aqueous ammonia added when the pH is neutral.
................................................................. cm³
[1]
(d) Compound H reacts with compound J to form a polymer.
Compound J has the formula HOCH₂CH₂OH.
(i) State the name of the –OH functional group in compound J.
................................................................. .................................................................
[1]
(ii) Ethene polymerises to form poly(ethene).
Choose one word from the list that best describes the type of reaction that occurs.
Draw a circle around the correct answer.
addition combustion cracking reduction
[1]
[Total: 12]

(a) Cement is made by heating a mixture of calcium carbonate and powdered clay.
(i) Choose from the list the name of the substance which contains calcium carbonate.
Draw a circle around the correct answer.
bauxite hematite limestone slaked lime [1]
(ii) The heat for this process is provided by burning natural gas.
Name the main constituent of natural gas.
.............................................................................................................................. [1]

(b) Complete the word equation for the thermal decomposition of calcium carbonate.
[2]

(c) Carbon dioxide is produced when dilute hydrochloric acid reacts with powdered calcium carbonate.
$$ ext{CaCO}_3 + 2 ext{HCl} ightarrow ext{CaCl}_2 + ext{CO}_2 + ext{H}_2 ext{O}$$
(i) Complete the diagram to show the apparatus used to investigate the volume of carbon dioxide produced during this reaction.
[2]
(ii) Name the piece of apparatus labelled M in the diagram.
.............................................................................................................................. [1]
(iii) Suggest the name of another piece of apparatus that can be used to measure the volume of carbon dioxide produced.
.............................................................................................................................. [1]
(iv) Describe the effect of each of the following on the rate of reaction of dilute hydrochloric acid with calcium carbonate.
• Large pieces of calcium carbonate are used instead of powdered calcium carbonate.
All other conditions stay the same.
..............................................................................................................................
• The temperature is decreased.
All other conditions stay the same.
.............................................................................................................................. [2]

(d) Explain how carbon dioxide contributes to climate change.
..............................................................................................................................
..............................................................................................................................
.............................................................................................................................. [2]

[Total: 12]

This question is about air.
(a) State the percentage of nitrogen in clean, dry air.
............................. % [1]

(b) Clean, dry air also contains argon. Argon is unreactive.
(i) Explain, using ideas about electronic structure, why argon is unreactive.
........................................................................................................................................
........................................................................................................................................ [1]
(ii) Give one use of argon.
........................................................................................................................................ [1]

(c) Carbon monoxide and oxides of nitrogen are pollutants of air.
For each of these pollutants state the source of the pollutant and an adverse effect of the pollutant.
source of carbon monoxide ........................................................................................................................................
adverse effect ........................................................................................................................................
source of oxides of nitrogen ........................................................................................................................................
adverse effect ........................................................................................................................................ [4]

Concentrated hydrochloric acid is electrolysed using carbon electrodes.
(a) State the products of this electrolysis at:
the negative electrode ......................................................................................................................
the positive electrode ......................................................................................................................
[2]
(b) Name a metal that can be used as an inert electrode instead of carbon.
..........................................................................................................................................................
[1]
(c) When dilute sulfuric acid is electrolysed, oxygen is produced at the positive electrode.
(i) Describe the separation and motion of the molecules in oxygen gas.
separation .........................................................................................................................................
..........................................................................................................................................................
motion ................................................................................................................................................
..........................................................................................................................................................
[2]
(ii) Describe a test for oxygen.
test ......................................................................................................................................................
observations ......................................................................................................................................
[2]

(a) The table shows some properties of five elements, P, Q, R, S and T.

Use only the elements shown in the table to answer these questions.

State which two of the elements, P, Q, R, S and T, have covalent molecules. Give two reasons for your answer.

(b) Diamond is a form of solid carbon.

(i) Describe the structure and bonding in diamond.   [2]

(ii) State why diamond is used for cutting tools.  [1]

(iii) Name one other form of solid carbon.  [1]

(c) Lithium is an element in Group I of the Periodic Table. Copper is a transition element.

Copper has a higher melting point and higher boiling point than lithium. Give two other ways in which the properties of transition elements differ from the properties of Group I elements.  [2]

(d) State whether lithium oxide is a basic oxide or an acidic oxide. Give a reason for your answer.   [1]

(e) The table compares the reactions of four metals with steam.

Put the four metals in order of their reactivity. Put the least reactive metal first.   [2]