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

The diagram shows the structures of five substances, A, B, C, D and E.
Answer the following questions using only the structures in the diagram. Each structure may be used once, more than once or not at all.
(a) Which structure, A, B, C, D or E,
(i) is an element, $\text{............................................................}$ [1]
(ii) has a structure similar to ethanol, $\text{..............................................}$ [1]
(iii) is a compound which contributes to acid rain, $\text{...............................}$ [1]
(iv) has double covalent bonds, $\text{....................................................}$ [1]
(v) contains halogen atoms? $\text{..............................................................}$ [1]
(b) Structure A is a non-metal. State three typical differences between metals and non-metals.
1 $\text{...............................................................................................................................}$
2 $\text{...............................................................................................................................}$
3 $\text{...............................................................................................................................}$ [3]
(c) Structure B is hydrogen sulfide. Hydrogen sulfide is a compound. What is meant by the term compound?
$\text{..........................................................................................................................................................}$
$\text{..........................................................................................................................................................}$ [1]

The diagram shows the composition of the planet Saturn.

(a) Describe how Saturn’s atmosphere differs from the Earth’s atmosphere. Give three differences.
1 ........................................................................................................
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2 ........................................................................................................
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3 ........................................................................................................
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[3]
(b) Some properties of hydrogen and helium are given in the table.
[Table_1]
(i) Use the information to suggest why the layer of liquid hydrogen in Saturn floats on top of the liquid helium.
..........................................................................................................
[1]
(ii) What is the physical state of hydrogen at -250°C? Explain your answer.
..........................................................................................................
..........................................................................................................
[2]

(c) The atmosphere of Saturn contains small amounts of ammonia.
(i) Describe a test for ammonia.
test .................................................................................................
result ...............................................................................................
[2]
(ii) Ammonia is a covalent compound.
Complete the diagram to show
• the arrangement of electrons in a molecule of ammonia,
• the symbols of the atoms present.
Show outer electrons only.

[2]

(d) Saturn’s atmosphere also contains small amounts of ammonium hydrosulfide.
Calculate the relative molecular mass of ammonium hydrosulfide, $NH_4SH$.
Use your Periodic Table to help you.
relative molecular mass = ...................................
[2]

(e) Saturn’s atmosphere also contains small amounts of methane. Small amounts of methane are present in the Earth’s atmosphere. Methane is a greenhouse gas.
(i) Name another greenhouse gas present in the Earth’s atmosphere.
............................................................................................
[1]
(ii) Scientists are concerned about the increase in the amount of greenhouse gases in the Earth’s atmosphere.
Explain why.
............................................................................................
[1]

The following compounds are present in a liquid used for cleaning metal.
ethanoic acid
ethanol
glycerol
sodium chloride
water

(a) (i) Draw the structure of the functional group present in ethanoic acid. [1]

(ii) Which one of the following pH values is acidic? Put a circle around the correct answer.
pH 4 pH 7 pH 9 pH 13 [1]

(iii) Ethanoic acid reacts with sodium hydroxide.
What type of reaction is this?
Put a circle around the correct answer.
neutralisation oxidation polymerisation reduction [1]

(iv) The reaction of ethanoic acid with sodium hydroxide is exothermic.
What is meant by the term \textit{exothermic}? [1]

(b) The structure of glycerol is shown.

Deduce the molecular formula of glycerol showing the number of carbon, hydrogen and oxygen atoms. [1]

(c) Balance the chemical equation for the incomplete combustion of ethanol.
$$C_2H_5OH + 2O_2 \rightarrow ......CO + ......H_2O$$ [2]

(d) (i) Describe a method of obtaining pure samples of both sodium chloride and water from aqueous sodium chloride. Explain why this method works. [3]

(ii) Which physical property could you measure to find out if a sample of water is pure? [1]

(iii) Sodium chloride contains chloride ions.
Describe a test for chloride ions.
test ............................................
result ............................................ [2]

The table shows the properties of four substances.

[Table_1]

(a) Complete the table to show the solubility in water of calcium iodide and the electrical conductivity of solid zinc.

(b) Give one piece of evidence from the table that shows that phosphorus is a simple covalent substance.
..........................................................................................................................

(c) What information in the table shows that sodium chloride is an ionic compound?
..........................................................................................................................
.....................................................................................................................

(d) Molten calcium iodide can be electrolysed.
Predict the products of this electrolysis at
the positive electrode (anode), ..............................................................
the negative electrode (cathode). ...................................................

(e) An atom of phosphorus has 31 nucleons.
Deduce the number of protons and neutrons present in one atom of phosphorus. Use your Periodic Table to help you.
number of protons .................................................................
number of neutrons .................................................................

(f) Phosphorus burns in an excess of air to form phosphorus(V) oxide.
Is phosphorus(V) oxide an acidic oxide or a basic oxide? Explain your answer.
..........................................................................................................................
......................................................................................................................

(g) Arsenic is in the same group of the Periodic Table as phosphorus.
Arsenic sublimes at 613 °C.
What is meant by the term sublimation?
..........................................................................................................................
......................................................................................................................

Nickel can be obtained from nickel(II) oxide by heating it with a mixture of carbon monoxide and hydrogen.

$$2NiO + CO + H_2 \rightarrow 2Ni + CO_2 + H_2O$$

(a) How does this equation show that the nickel(II) oxide is reduced?
......................................................................................................................... [1]

(b) Nickel can be purified by reacting impure nickel with carbon monoxide.
A compound called tetracarbonylnickel, Ni(CO)$_4$, is formed.

$$Ni + 4CO \rightleftharpoons Ni(CO)_4$$

What is the meaning of the symbol $\rightleftharpoons$?
......................................................................................................................... [1]

(c) The tetracarbonylnickel is heated to obtain pure nickel.

$$Ni(CO)_4 \rightarrow Ni + 4CO$$

(i) Suggest why the nickel obtained can be separated easily from the carbon monoxide.
......................................................................................................................... [1]
(ii) State one adverse effect of carbon monoxide on health.
......................................................................................................................... [1]

(d) Nickel is a transition element. Potassium is a Group I element.

(i) Describe two differences in the physical properties of nickel and potassium.
1 .......................................................................................................................
.........................................................................................................................
2 .......................................................................................................................
.........................................................................................................................
[2]

(ii) Describe one difference in the properties of nickel(II) chloride and potassium chloride.
......................................................................................................................... [1]

(e) The properties and relative reactivity with water of some Group I elements are shown in the table.

[Table]

(i) Complete the table
⚫ to predict the boiling point of rubidium,
⚫ for the relative reactivity of rubidium with water.
[2]

(ii) Describe the general trend in the density of the Group I elements.
......................................................................................................................... [1]

Ethanol can be manufactured from ethene or by the fermentation of glucose.

(a) Describe these two methods of manufacturing ethanol.

In your answer, include
• the names of any additional substances needed,
• the reaction conditions.

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...................................................................................................................... [5]

(b) Ethene is an unsaturated hydrocarbon.

(i) Describe how you could distinguish between an unsaturated hydrocarbon and a saturated hydrocarbon using aqueous bromine.

......................................................................................................................
......................................................................................................................
...................................................................................................................... [2]

(ii) Ethene molecules can form polymers.

Which phrase describes a polymer?
Tick one box.

a giant structure containing one type of atom [ ]
a large molecule formed by cracking monomers [ ]
a large molecule formed by the addition of many ions [ ]
a large molecule formed from many monomers [ ]
[1]

(iii) Terylene is a polymer.
Give one use of Terylene.

...................................................................................................................... [1]

Sulfur dichloride, $SCl_2$, is a red liquid which vaporises easily at room temperature and pressure.
(a) A drop of sulfur dichloride was placed in the corner of a glass box.
The glass box was closed and left for 12 hours.
After 12 hours a red vapour had spread to fill the whole box.

Explain these observations using the kinetic particle model.
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........................................................................................................................................ [3]
(b) Sulfur dichloride can be made by passing chlorine through liquid disulfur dichloride, $S_2Cl_2$.
Complete the chemical equation for this reaction.
$S_2Cl_2 + \text{..........} \rightarrow \text{......}SCl_2$
....................................................................................................................................... [2]
(c) Some changes of state of sulfur dichloride are shown.

Name the changes of state represented by $P$ and $Q$.
$P$ ............................................................................................................
$Q$ ............................................................................................................ [2]

Calcium carbonate (limestone) decomposes when heated.

\( \text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2 \)

(a) When 20.0 g of calcium carbonate are decomposed, 11.2 g of calcium oxide (lime), CaO, are formed.

Calculate the mass of calcium oxide formed when 160.0 g of calcium carbonate are decomposed.

\( \underline{\text{............................ g}} \) [1]

(b) The graph shows the volume of carbon dioxide produced when some small pieces of calcium carbonate are heated and decompose.



(i) Deduce the volume of carbon dioxide produced during the first 20 minutes of the decomposition.

.................................................................................................................................... [1]

(ii) At what time was the reaction complete?

.................................................................................................................................... [1]

(iii) What would be the effect, if any, on the rate of reaction if the same mass of powdered calcium carbonate were used?

............................................................................................................................ [1]

(c) The table shows how limestone is used.

[Table_1]

(i) What percentage of limestone is used in agriculture?

......................................................................................................................................... [1]

(ii) Limestone and lime are used in agriculture.

Why is lime used in agriculture?

.........................................................................................................................................
......................................................................................................................................... [2]