Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2017 Summer Zone 2

(a) The electronic structures of five atoms, A, B, C, D and E, are shown.
Answer the following questions about these atoms. Each atom may be used once, more than once or not at all.
Which atom, A, B, C, D or E,
(i) has a total of 8 electrons, ....................................... [1]
(ii) is in Group III of the Periodic Table, ....................................... [1]
(iii) has 13 protons, ....................................... [1]
(iv) is a noble gas, ....................................... [1]
(v) forms a stable ion with a single negative charge? ....................................... [1]

(b) Complete the table to show the number of electrons, neutrons and protons in the sulfur atom and oxide ion shown.
[Table_1]
\( \begin{array}{|c|c|c|c|} \hline & \text{number of electrons} & \text{number of neutrons} & \text{number of protons} \\ \hline {}^{34}_{16}S & 16 & & \\ \hline {}^{18}_{8}O^{2-} & & 10 & \\ \hline \end{array} \)
[3]

(a) The table shows the ions present in a 1000 cm³ sample of rainwater.

[Table_1]

Answer these questions using the information from the table.

(i) State the name of the ion Cl⁻.
................................................................................................................................... [1]

(ii) Which positive ion is present in the highest concentration?
................................................................................................................................... [1]

(iii) Calculate the mass of potassium ions present in 200 cm³ of this sample.

mass of potassium ions = .......................................... mg [1]

(iv) Calculate the mass of solid formed when all the water is evaporated from the 1000 cm³ sample.

mass of solid formed = .......................................... mg [1]

(v) Name the compound containing Na⁺ ions and HCO₃⁻ ions.
................................................................................................................................... [1]

(b) Describe a test for potassium ions.
test ....................................................................................................................
result ....................................................................................................................
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(c) The formulae of some nitrates are given.

aluminium nitrate, Al(NO₃)₃
magnesium nitrate, Mg(NO₃)₂
sodium nitrate, NaNO₃
Deduce the formula for potassium nitrate.
......................................................................................................................... [1]

(d) Molten potassium bromide can be electrolysed using inert electrodes.

Predict the products of this electrolysis at
the negative electrode (cathode), .......................................
the positive electrode (anode). .........................................
..................................................................................................................................... [2]

The diagram shows part of the structures of three substances, X, Y and Z, at room temperature and pressure.

(a) Describe substances X, Y and Z in terms of
• their bonding,
• the arrangement of their particles,
• the motion of their particles.
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(b) A closed gas syringe contains substance Z.

Describe what happens to the volume of substance Z in the syringe when the temperature is increased. The pressure remains constant. Explain your answer in terms of particles.
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(c) Describe the colour change when substance Y is added to anhydrous copper(II) sulfate.
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(d) Give a reason why substance Y is a compound.
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Aluminium and zinc are both metals. Aluminium is extracted from its purified ore by electrolysis.
(a) (i) State the name of an ore of aluminium.
........................................................... [1]
(ii) Explain why aluminium is extracted from its purified ore by electrolysis and not by heating with carbon.
...........................................................[1]

(b) Aluminium reacts with hydrochloric acid to form aluminium chloride and a gas which 'pops' with a lighted splint.
(i) Identify this gas.
...........................................................[1]
(ii) Suggest a practical method for investigating the rate of this reaction involving collection of the gas. You may include a labelled diagram in your answer.
...........................................................[3]

(c) State one use of aluminium. Give a reason why it is used for this purpose.
use ...........................................................[2]


(d) Give two advantages of recycling aluminium.
1 ...........................................................
2 ........................................................... [2]


(e) Zinc is extracted from zinc oxide by heating zinc oxide with carbon monoxide.
$$ \text{ZnO + CO} \rightarrow \text{Zn + CO}_2 $$
(i) How does this equation show that zinc oxide is reduced?
...........................................................[1]
(ii) The energy level diagram for this reaction is shown.

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

(a) (i) On the structure shown draw a circle around the carboxylic acid functional group. [1]
(ii) State the name of one other functional group found in lactic acid. .............................................................................................................................. [1]
(b) Give the molecular formula of lactic acid showing the number of carbon, hydrogen and oxygen atoms. .............................................................................................................................. [1]
(c) Complete the structure of ethanol. Show all of the atoms and all of the bonds.
[2]
(d) The table shows the properties of some alcohols.
[Table_1]
(i) What is the meaning of the term volatility? .............................................................................................................................. [1]
(ii) Which alcohol in the table has the highest melting point? .............................................................................................................................. [1]
(iii) Predict the boiling point of ethanol. ............................................................................................................................. [1]
(iv) What is the state of propanol at 120°C? Explain your answer. ............................................................................................................................. ............................................................................................................................. [2]
(e) (i) Complete this chemical equation for the incomplete combustion of methanol.
CH$_3$OH + ............. → CO + ......H$_2$O [2]
(ii) Calculate the relative molecular mass of methanol, CH$_3$OH. Show all your working. Use your Periodic Table to help you.
relative molecular mass = ...................................... [2]

(a) The table shows the properties of some types of steel.
[Table_1: type of steel, density in g/cm^3, resistance to corrosion, relative strength, relative hardness]
Which type of steel, L, M or N, would be best to reinforce concrete? Give two reasons for your answer.
type of steel ...............
reason 1 ....................................................................................................................
reason 2 ....................................................................................................................

(b) Steel is an alloy.
Which diagram, P, Q, R or S, represents an alloy?
[Image_1: Diagrams labeled P, Q, R, S with different arrangements of Fe, C, S]
..............................................................................................................................

(c) Iron is a transition element.
State three properties of transition elements which are not shown by Group I elements.
1 .........................................................................................................................
2 .........................................................................................................................
3 .........................................................................................................................

(d) Iron reacts with hydrochloric acid to form iron(II) chloride and hydrogen.
Complete the chemical equation for this reaction.
$Fe + ......HCl \rightarrow FeCl_2 + ...............$

(e) Some information about the reaction of four metals with oxygen is given.
copper: surface turns black slowly when heated strongly
iron: thin wire burns when heated strongly
gold: remains a gold color when heated strongly
potassium: bursts into flame when heated gently
List these metals in order of their reactivity. Put the least reactive metal first.
least reactive -----------------> most reactive

(f) The table compares the time taken for reaction of iron with methanoic acid, phosphoric acid and propanoic acid, each at three different concentrations. The time taken for the iron to decrease in mass by 1.0 g was measured. All other conditions were kept the same.
[Table_2: time taken for reaction /hours according to acid concentration with methanoic, phosphoric, and propanoic acid]
(i) How does the concentration of acid affect the rate of reaction?
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(ii) Which acid reacts most rapidly with the iron?
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(iii) Predict how long it would take for the iron to decrease in mass by 1.0 g using propanoic acid of concentration 0.03 mol/dm^3.
time taken = ...................................... hours
(iv) Suggest which one of these pH values is the pH of concentrated aqueous phosphoric acid. Draw a circle around the correct answer.
pH 2 pH 7 pH 9 pH 13

Sulfur is an element in Group VI of the Periodic Table.
(a) What is the meaning of the term *element*?
..................................................................................................................................................................................................................... [1]

(b) Give one source and one use of sulfur.
source .................................................................................................................................................................................
use ................................................................................................................................................................................... [2]

(c) When sulfur vapour touches a cold surface it changes directly to a solid.
What is the name given to this change of state?
............................................................................................................................................................................................. [1]

(d) Sulfur dioxide and oxides of nitrogen are both atmospheric pollutants.
• Give the sources of these gases.
• Describe the effects of these pollutants on the environment.
• Describe the effects of these pollutants on health.
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(e) Sulfur and zinc are both insoluble in water.
Sulfur does not react with hydrochloric acid but zinc reacts to form a soluble salt and a gas which escapes into the air.
Suggest how you could prepare a pure dry sample of sulfur from a mixture of sulfur powder and zinc powder.
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