Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2019 Summer Zone 2

The diagrams show part of the structures of five substances, A, B, C, D and E.

(a) Answer the following questions about these structures.
Each structure may be used once, more than once or not at all.
State which one of these structures, A, B, C, D or E:
(i) is an alcohol
............................................................................................................................ [1]
(ii) is an ionic compound
............................................................................................................................ [1]
(iii) conducts electricity when solid
............................................................................................................................ [1]
(iv) contributes to acid rain
............................................................................................................................ [1]
(v) reacts with an acid to form a salt and water.
............................................................................................................................ [1]
(b) Substance E is a compound.
What is meant by the term compound?
............................................................................................................................ [1]

(a) Iron can be converted into steel in a basic oxygen converter. Oxygen is blown into the impure molten iron to remove some of the impurities.
(i) Oxygen reacts with the carbon in the impure iron to form carbon dioxide. Write a chemical equation for this reaction.
.......................................................... [2]
(ii) Basic oxides in the lining of the converter react with impurities such as sulfur dioxide to form slag. What type of oxide is sulfur dioxide? Give a reason for your answer.
.......................................................... [2]

(b) Iron(III) chloride, $\text{Fe}_2\text{Cl}_6$, is produced when iron is heated with chlorine. The diagram shows the apparatus used.
(i) Draw an arrow on the diagram to show where the apparatus is heated.
[1]
(ii) Iron(III) chloride undergoes sublimation. What is meant by the term \textit{sublimation}?
.......................................................... [1]
(iii) Suggest why the iron(III) chloride is collected in the flask and \textit{not} in the ceramic boat.
.......................................................... [2]
(iv) At higher temperatures, iron(III) chloride decomposes. $\text{Fe}_2\text{Cl}_6 \overset{\text{heat}}{\longrightarrow} 2\text{FeCl}_2 + \text{Cl}_2$
Explain why this is a decomposition reaction.
.......................................................... [2]

(c) Iron reacts with chlorine and \textit{other} halogens. Name \textit{two} other substances which react with iron.
1 .......................................................... [1]
2 .......................................................... [1]

(d) Describe a test for iron(II) ions.
test ..........................................................
observations .......................................................... [2]

(a) The table shows the percentage by mass of the elements in the Earth’s crust and in the oceans.

[Table_1]

Answer these questions using only the information in the table.

(i) Deduce the percentage by mass of other elements present in the oceans.
............................... % [1]

(ii) Which element is present in the Earth’s crust in the greatest percentage by mass?
...................................................................................................................................... [1]

(iii) Give two major differences in the percentage by mass of the elements in the Earth’s crust and in the oceans.
1 .........................................................................................................................................
....................................................................................................................................................

2 .........................................................................................................................................
.................................................................................................................................................... [2]
displays the mentioned table in the question.

(b) Aluminium oxide is a compound present in aluminium ore.

(i) Name an ore which contains aluminium oxide.
..................................................................................................................................... [1]

(ii) Predict the products of the electrolysis of molten aluminium oxide at:
the positive electrode ...........................................................................................................
the negative electrode ......................................................................................................... [2]

(iii) Suggest why aluminium is extracted by electrolysis and \textbf{not} by reduction with carbon.
........................................................................................................................ [1]

This question is about bromine and compounds of bromine.

(a) Use the kinetic particle model to describe the arrangement and type of motion of the molecules in:

• liquid bromine ..........................................................
..........................................................................................................................
..........................................................................................................................

• bromine gas ..........................................................
..........................................................................................................................
......................................................................................................................... [4]

(b) The graph shows how the volume of bromine gas changes with temperature. The pressure is kept constant.



Describe how the volume of the bromine gas changes with temperature.
..........................................................................................................................
.......................................................................................................................... [1]

(c) (i) Complete the word equation to show the halogen and halide compound which react to form the products bromine and potassium chloride.



........................................ + ........................................ → bromine + potassium chloride
........................................

[2]

(ii) Explain, in terms of the reactivity of the halogens, why aqueous bromine will not react with aqueous potassium chloride.
..........................................................................................................................
......................................................................................................................... [1]

(d) Bromine reacts with hydrogen sulfide, H$_2$S.

(i) Complete the chemical equation for this reaction.
....... + H$_2$S → ......HBr + S

[2]

(ii) The energy level diagram for this reaction is shown.



Explain how this diagram shows that the reaction is exothermic.
..........................................................................................................................
......................................................................................................................... [1]

(e) Describe a test for bromide ions.
test ..........................................................................................................................
observations ............................................................................................................ [2]

(a) Draw the structure of a molecule of ethane. Show all of the atoms and all of the bonds.

(b) Which one of these compounds belongs to the same homologous series as methane? Draw a circle around the correct answer. butane methanoic acid methanol propene

(c) Ethene can be manufactured by cracking.
(i) Complete the sentence about cracking using words from the list.
atoms ions larger molecules reactive smaller
Cracking is the process of breaking down ............... alkane .................. into ............... alkanes and alkenes. [2 marks]
(ii) State two conditions needed for cracking.
1 ........................................................
2 ........................................................ [2 marks]

(d) Poly(ethene) is made by the polymerisation of ethene. Which one of the structures represents part of a poly(ethene) molecule? Tick one box.

(e) Nylon is also a polymer.
(i) Give one common use of nylon. [1 mark]
(ii) Part of the structure of nylon is shown.
How many different types of atom are shown in this structure? [1 mark]

(f) The structure of a monomer used to make a polymer is shown.
(i) What structural feature of this molecule shows that it is unsaturated? [1 mark]
(ii) Describe a test to show that this compound is unsaturated.
test ....................................................
observations .................................................... [2 marks]

This question is about cobalt and compounds of cobalt.

(a) Describe how you could prepare a pure sample of crystals of hydrated cobalt(II) sulfate using dilute sulfuric acid and an excess of cobalt(II) carbonate.
........................................................................................................................................
........................................................................................................................................
........................................................................................................................................
........................................................................................................................................ [3]

(b) Complete the table to calculate the relative formula mass of anhydrous cobalt(II) sulfate, CoSO₄.
Use your Periodic Table to help you.

| type of atom | number of atoms | relative atomic mass |
|-------------|-----------------|----------------------|
| cobalt | | |
| sulfur | 1 | 32 | 1 x 32 = 32
| oxygen | | |

relative formula mass = ..................................... [2]

(c) Complete the table to show the number of electrons, protons and neutrons in the oxygen atom and cobalt ion shown.

| | number of electrons | number of neutrons | number of protons |
|---------------- | ------------------- | ----------------- | ----------------- |
| $$^{17}_{8}\text{O}$$ | | | |
| $$^{59}_{27}\text{Co}^{2+}$$ | | | 27 |

[4]

(d) Anhydrous cobalt(II) chloride is used to test for water.
State the colour change when water is added to anhydrous cobalt(II) chloride.
from ........................................................ to ...........................................................
[2]

(e) An alloy of cobalt, chromium and molybdenum is used to make cutlery.

(i) Which one of the following diagrams best represents the structure of the alloy?
Draw a circle around the correct answer.


A             B             C             D [1]

(ii) Which one of these substances is also used to make cutlery?
Tick one box.

□ mercury
□ sodium
□ stainless steel
□ graphite [1]

A student investigates the rate of reaction of magnesium ribbon with an excess of dilute hydrochloric acid.
$$\text{Mg + 2HCl} \rightarrow \text{MgCl}_2 + \text{H}_2$$
(a) Name the salt formed when magnesium reacts with dilute hydrochloric acid.
..............................................................................................................[1]

(b) The graph shows how the volume of hydrogen produced changes with time.

(i) Describe how the rate of reaction changes with time. Use the graph to explain your answer.
..............................................................................................................
..............................................................................................................
..............................................................................................................[2]
(ii) How many seconds did it take to collect the first 25 \text{cm}^3 of hydrogen?
................................. s [1]
(iii) The experiment is repeated at a higher temperature. All other conditions are kept the same.
Draw a line on the grid for the experiment using a higher temperature. [2]

(iv) If 2.4g of magnesium is used, 0.2g of hydrogen is produced.
Calculate the mass of magnesium needed to produce 0.8g of hydrogen using an excess of dilute hydrochloric acid.
mass of magnesium = ................................. g [1]

(a) Oxides of nitrogen are pollutants in the air.
(i) One source of oxides of nitrogen in the air is from the manufacture of nitric acid.
State one other source of oxides of nitrogen in the air.
.................................................................................................................................... [1]
(ii) State one adverse effect of oxides of nitrogen on health.
.................................................................................................................................... [1]
(iii) Oxides of nitrogen act as catalysts.
What is meant by the term catalyst?
....................................................................................................................................
.................................................................................................................................... [1]
(iv) Oxides of nitrogen are formed during the manufacture of nitric acid.
Which one of the pH values could be the pH of nitric acid?
Draw a circle around the correct answer.
pH 1 pH 7 pH 10 pH 14 [1]

(b) Nitrogen is present in fertilisers.
Why are fertilisers added to the soil where crops are grown?
.................................................................................................................................... [1]

(c) The table shows some observations about the reactivity of four metals with dilute hydrochloric acid.