Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2016 Winter Zone 1

The diagram shows part of the Periodic Table.

Answer the following questions using only the elements in the diagram. Each element may be used once, more than once or not at all.
(a) Which element
(i) has a smaller proton number than lithium, ............................................................................................................ [1]
(ii) is formed at the cathode when a dilute solution of sulfuric acid is electrolysed, ............................................................................................................ [1]
(iii) has an oxide of the type $XO_2$ which is used to bleach wood pulp, ............................................................................................................ [1]
(iv) forms ions which when tested with excess aqueous sodium hydroxide produce a white precipitate, ............................................................................................................ [1]
(v) is extracted from bauxite? ............................................................................................................ [1]

(b) Mercury has several naturally-occurring isotopes. One of these is shown. $$ \begin{align} ^{204}_{80} \text{Hg} \end{align} $$ (i) What is the meaning of the term “isotope”? .............................................................. .............................................................. [2]
(ii) How many neutrons are there in one atom of the isotope $^{204}_{80} \text{Hg}$?
.............................................................. [1]
(iii) How many protons are there in one atom of the isotope $^{204}_{80} \text{Hg}$?
.............................................................. [1]
(iv) Determine the number of electrons in the mercury(II) ion, $\text{Hg}^{2+}$.
.............................................................. [1]

The bar charts compare the concentrations of the main ions in two samples of seawater, sample A and sample B.

(a) Use the information in the bar charts to answer the following questions.
(i) Describe two differences in the composition of the seawater in sample A and sample B.
................................................................................................................................................................................
................................................................................................................................................................................ [2]
(ii) Which positive ion has the lowest concentration in sample A?
................................................................................................................................................................................ [1]
(iii) Calculate the mass of sodium ions in 200 cm$^3$ of sample B. Show all your working. [1 dm$^3$ = 1000 cm$^3$]
mass = .................... mg [2]
(b) Describe a test for sodium ions.
test ..............................................................................................................................................................
result ............................................................................................................................................................ [2]

(c) River water contains small particles of clay. When these particles are viewed under a microscope they show a random, jumpy motion even when the water is still.
What name is given to this type of movement?
................................................................................................................................................................................ [1]

(d) Carbon dioxide dissolves in water to form a mixture which contains hydrogencarbonate ions and hydrogen ions.
$$ \text{CO}_2(g) + \text{H}_2\text{O}(l) \rightleftharpoons \text{HCO}_3^- (aq) + \text{H}^+ (aq) $$
(i) What is the meaning of the symbol $\rightleftharpoons$?
................................................................................................................................................................................ [1]
(ii) The solution formed is slightly acidic.
Describe how you would use Universal Indicator paper to determine the pH of this solution.
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................................................................................................................................................................................ [2]
(iii) Carbon dioxide is a greenhouse gas which causes climate change.
Explain how carbon dioxide contributes to climate change.
................................................................................................................................................................................ [1]
(iv) State the name of one other greenhouse gas and give one source of this gas.
gas .................................................................................................................................................................
source ............................................................................................................................................................ [2]

Calcium is in Group II of the Periodic Table.
(a) Draw a diagram to show the electronic structure of an atom of calcium. [2]
(b) Calcium is manufactured by the electrolysis of molten calcium chloride.
Complete the boxes in the diagram to show the
• anode,
• cathode,
• electrolyte. [2]
(c) Calcium reacts with water to form calcium hydroxide and a gas which 'pops' with a lighted splint.
Complete the chemical equation for this reaction.
Ca + .......H$_2$O → Ca(OH)$_2$ + ........... [2]
(d) Describe the manufacture and uses of lime (calcium oxide).
Include at least one relevant word equation relating to the manufacture or use of lime. [4]

A porous pot has tiny holes in its walls which allow gases to move in or out of the pot. A teacher filled a porous pot with green chlorine gas. The teacher then placed the pot in a large jar of air. After 10 minutes, a green colour was seen outside the porous pot.
(a) Use the kinetic particle model of matter to explain this observation.
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........................................................................................................................ [3]
(b) A porous barrier can be used to separate uranium fluoride molecules containing different isotopes of uranium.
(i) State the main use of the radioactive isotope $^{235}U$.
........................................................................................................................
[1]
(ii) Give one medical use of radioactive isotopes.
........................................................................................................................
[1]
(iii) The accurate relative atomic mass of uranium is 238.03.
Define the term relative atomic mass.
........................................................................................................................
........................................................................................................................
[2]

(c) Chlorine reacts with potassium bromide to form bromine and potassium chloride.
(i) Complete the chemical equation for this reaction.
............. + 2KBr $\rightarrow$ Br$_2$ + ........KCl
[2]
(ii) Give one use of chlorine.
........................................................................................................................
[1]
(iii) Chlorine forms an oxide with the formula Cl$_2$O$_7$.
Is this oxide an acidic or a basic oxide? Explain your answer.
........................................................................................................................
........................................................................................................................
[1]
(iv) A teacher heated a test-tube containing anhydrous copper(II) chloride. A piece of damp litmus paper was placed at the top of the test-tube.
The anhydrous copper(II) chloride decomposed and chlorine was formed.
Describe the colour change of the litmus paper.
........................................................................................................................
[1]

Use the information in the table to answer the following questions.
(a) (i) What is the relationship between the percentage of carbon in the steel and its strength? ......................................................................................................................................................... [1]
(ii) State whether there is a relationship between the percentage of carbon in the steel and its melting point range. Explain your answer. ......................................................................................................................................................... .......................................................................................................................................................... [1]
(iii) Which steel would be best to use for making a bicycle chain? Explain your answer. ......................................................................................................................................................... .......................................................................................................................................................... [1]

(b) Steel is an alloy.
Which one of the diagrams best represents an alloy? Draw a ring around the correct answer. [1]

(c) High voltage electricity cables are made from aluminium with a steel core.
(i) Apart from conducting electricity, what is the purpose of the steel core? ......................................................................................................................................................... [1]
(ii) Aluminium is a good electrical conductor.
Give one other use of aluminium and state a property of aluminium which makes it suitable for this use.
use .....................................................................................................................................
property .......................................................................................................................................................... [2]

(d) Aluminium powder reacts with powdered iron(III) oxide. The equation for this reaction is shown.
$$2Al + Fe_2O_3 \rightarrow Al_2O_3 + 2Fe$$
(i) Which substance is oxidised in this reaction? Explain your answer. ......................................................................................................................................................... .......................................................................................................................................................... [2]
(ii) The energy level diagram for this reaction is shown.
Is this reaction exothermic or endothermic? Explain your answer. ......................................................................................................................................................... .......................................................................................................................................................... [1]

(a) Describe the characteristic properties of acids.
In your answer you should refer to the reactions of acids with metals, bases, carbonates and indicators.
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[5]

(b) The table shows some properties of the first five members of the carboxylic acid homologous series.

acid           molecular formula    melting point / °C   boiling point / °C      density in g/cm³
methanoic acid      CH₂O₂                          8                  101                    1.22
ethanoic acid      C₂H₄O₂                         17                   118                     1.05
propanoic acid      C₃H₆O₂                       −21                  141                    0.99
butanoic acid      C₄H₈O₂                       −5                    164                     0.96
pentanoic acid      C₅H₁₀O₂                    −34                   

(i) How does the density of the carboxylic acids vary with the number of carbon atoms in the molecule?
............................................................................................................................................................................. [1]

(ii) Suggest a value for the boiling point of pentanoic acid.
............................................................................................................................................................................. [1]

(iii) Determine the state of ethanoic acid at 15°C.
Explain your answer.
............................................................................................................................................................................. [2]

(iv) Draw the structure of the functional group present in carboxylic acids.
Show all of the atoms and all of the bonds.
[1]

(v) Calculate the relative molecular mass of butanoic acid.
Show all your working.
[2]

(c) Identify the following as either physical changes or chemical changes by writing either ‘physical’ or ‘chemical’ in the spaces provided.
The condensation of ethanoic acid vapour to liquid ethanoic acid is a ......................... change.
The reaction of sodium with ethanoic acid is a ......................... change.
The dissolving of a salt in water is a ......................... change.
[2]

The diagram shows the changes of state when sulfur is heated.
(a) Give the names of the changes of state labelled A and B.
A .................................................................................................................................................
B ................................................................................................................................................. [2]
(b) Describe the arrangement and motion of the particles in sulfur vapour.
arrangement ................................................................................................................................
motion ............................................................................................................................................ [2]
(c) Give one use of sulfur.
..................................................................................................................................................... [1]
(d) Some compounds of sulfur are found in coal.
Explain why the presence of sulfur in coal has an adverse effect on human health when the coal is burnt.
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..................................................................................................................................................... [2]
(e) One of the compounds of sulfur in coal is thiophene. The structure of thiophene is shown.
(i) Determine the formula of thiophene.
..................................................................................................................................................... [1]
(ii) Thiophene can be made in the laboratory by heating ethyne, $C_2H_2$, with hydrogen sulfide, $H_2S$, in the presence of a catalyst.
What is the purpose of the catalyst?
..................................................................................................................................................... [1]
(iii) When 2.6 g of ethyne react with excess hydrogen sulfide, 4.2 g of thiophene are formed.
Calculate the mass of thiophene formed when 15.6 g of ethyne react with excess hydrogen sulfide.
..................................................................................................................................................... [1]