Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2019 Winter Zone 1

This question is about solids, liquids and gases.
(a) The list gives the names of nine substances which are solids at room temperature.
a ceramic
aluminium
anhydrous cobalt(II) chloride
anhydrous copper(II) sulfate
calcium oxide
graphite
iodine
iron
sodium
Answer the following questions about these substances. Each substance may be used once, more than once or not at all.
State which substance:
(i) turns pink when water is added to it ................................................................................................................... [1]
(ii) is a non-metal which is used as a lubricant ................................................................................................................... [1]
(iii) is used to neutralise acidic industrial waste ................................................................................................................... [1]
(iv) is extracted from bauxite ................................................................................................................... [1]
(v) is used as an electrical insulator. ................................................................................................................... [1]
(b) Some changes of state of sodium are shown.

(i) State the names of the changes of state represented by A and B.
A ..........................................................................................................
B .......................................................................................................... [2]
(ii) Use the kinetic particle model to describe the arrangement and separation of the particles in:
solid sodium ...........................................................................................
.....................................................................................................................
.....................................................................................................................
liquid sodium. .........................................................................................
.....................................................................................................................
..................................................................................................................... [4]

Biogas is made by fermenting animal and vegetable waste.
(a) The table shows the percentage composition of the gases present in a sample of biogas.

[Table_1: | substance present | percentage present in biogas | |------------------|----------------------------| | carbon dioxide | 28.5 | | hydrogen | 1.0 | | methane | 62.0 | | nitrogen | | | water vapour | 2.4 | | other substances | 0.1 | | total | 100.0 | ]

Deduce the percentage of nitrogen present in this sample of biogas.
.....................................................................................................

(b) (i) Balance the chemical equation for the complete combustion of methane.
$$CH_4 + .....O_2 \rightarrow CO_2 + .....H_2O$$ [2]

(ii) Which one of these compounds belongs to the same homologous series as methane?
Draw a circle around the correct answer.
methanoic acid methanol propane propanol propene [1]

(iii) Methane is present in the refinery gas fraction produced by the fractional distillation of petroleum.
Match the fractions on the left with their uses on the right.
The first one has been done for you.

[Image_1: | fraction | use | |--------------------|----------------------------------| | refinery gas | making roads | | fuel oil fraction | making chemicals | | bitumen | fuel for heating and cooking | | naphtha fraction | fuel for ships | ]
[2]

(c) (i) Draw a dot-and-cross diagram to show the electron arrangement in a molecule of hydrogen. [1]

(ii) State one use of hydrogen.
..................................................................................................... [1]

(d) The biogas contains a small amount of compound C.
The structure of compound C is shown.

[Image_2: H | H-N-C=O | H-C-H | S
]

(i) On the structure shown, draw a circle around the carboxylic acid functional group. [1]

(ii) How many different types of atoms are present in compound C?
..................................................................................................... [1]

(e) Describe the manufacture of ethanol by fermentation.
In your answer include:
• the names of the substances needed for fermentation
• the conditions needed for fermentation.
.....................................................................................................
.....................................................................................................
.....................................................................................................
.....................................................................................................
.....................................................................................................
.....................................................................................................
..................................................................................................... [4]

A student investigated the reaction between zinc carbonate and an excess of dilute hydrochloric acid.

$\text{ZnCO}_3 + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{CO}_2 + \text{H}_2\text{O}$

The rate of reaction can be found by measuring the decrease in the mass of the reaction mixture over time.

(a) Describe one other practical method for measuring the rate of this reaction.

..............................................................................................................................................................
..............................................................................................................................................................
..............................................................................................................................................................
..............................................................................................................................................................
.............................................................................................................................................................. [3]

(b) When 6.25 g of zinc carbonate is used, 2.20 g of carbon dioxide is formed.

Calculate the mass of zinc carbonate that forms 11.00 g of carbon dioxide.

..............................................................................................................................................................

mass of zinc carbonate = ............................................. g [1]

(c) What effect do the following have on the rate of this reaction?

• Decreasing the temperature of the reaction mixture.
All other conditions are kept the same.
..............................................................................................................................................................

• Increasing the concentration of hydrochloric acid.
All other conditions are kept the same.
..............................................................................................................................................................
[2]

(d) Carbon dioxide is formed:

• when an acid reacts with a carbonate
• as a product of the complete combustion of carbon-containing substances.

State two other sources of carbon dioxide.

1 ........................................................................................................................................................
2 ........................................................................................................................................................
[2]

An isotope of sodium is written as shown.
$$^{23}_{11} \text{Na}$$
(a) (i) Deduce the number of protons, electrons and neutrons in this isotope of sodium.
number of protons ..............................................................
number of electrons ..........................................................
number of neutrons .......................................................... [3]
(ii) State \textit{one} medical use of radioactive isotopes.
........................................................................................... [1]
(b) (i) Draw the electronic structure of a sodium atom. [2]
(ii) State the name of the particle which is lost when a sodium atom forms a sodium ion.
........................................................................................... [1]
(c) Sodium reacts with water to form:
• an alkaline solution
• a gas which ‘pops’ with a lighted splint.
(i) Complete the word equation for the reaction of sodium with water.
$$\text{sodium} + \text{water} \rightarrow \text{.................................} + \text{.................................}$$ [2]
(ii) The reaction of sodium with water is exothermic. What is meant by the term \textit{exothermic}?
...........................................................................................
........................................................................................... [1]
(iii) Sodium reacts with oxygen to form sodium oxide. Is sodium oxide an acidic oxide or a basic oxide? Give a reason for your answer.
...........................................................................................
........................................................................................... [1]
(d) The table shows some observations for the reaction of four metals with cold water and with hot water.
[Table]
Use this information to put the \textit{four} metals in order of their reactivity. Put the least reactive metal first.
least reactive ..................................................... most reactive [2]

This question is about the halogens and compounds of the halogens.

(a) The properties of some halogens are shown in the table.

[Table_1]

(i) Complete the table to estimate:
- the density of liquid chlorine
- the boiling point of iodine. [2]

(ii) Describe the trend in the atomic radius of the halogens down the group.
........................................................................................................................ [1]

(iii) Predict the physical state of bromine at 50°C.
Give a reason for your answer.
........................................................................................................................
........................................................................................................................
........................................................................................................................ [2]

(b) Bromine reacts with an aqueous potassium salt to form iodine and a different potassium salt.
Complete the word equation for this reaction.

[2]

(c) Fluorine is above chlorine in Group VII of the Periodic Table.

(i) Explain, using ideas about the reactivity of the halogens, why chlorine does not react with aqueous sodium fluoride.
..........................................................................................................................
.......................................................................................................................... [1]

(ii) Balance the chemical equation for the reaction of fluorine with ammonia.
.....NH_3 + .....F_2 → N_2 + 6HF [2]

(iii) A compound of fluorine has the formula XeO_3F_2.
Complete the table to calculate the relative molecular mass of XeO_3F_2.
Use your Periodic Table to help you.

[Table_2]

relative molecular mass = ................................ [2]

(iv) The compound XeO_3F_2 readily undergoes reduction.
What is meant by the term reduction?
..........................................................................................................................
[1]

This question is about ammonia.

(a) When ammonia gas reacts with hydrogen chloride gas, white fumes of ammonium chloride are formed.

$$ \text{NH}_3 + \text{HCl} \rightarrow \text{NH}_4\text{Cl} $$

(i) What type of chemical reaction is this?
Draw a circle around the correct answer.

decomposition neutralisation oxidation reduction [1]

(ii) Watch-glasses of aqueous ammonia and concentrated hydrochloric acid were placed near each other on a table.
At first no white fumes were seen.
After a short time, white fumes were seen between the watch-glasses.



Explain these observations using the kinetic particle model.

..............................................................................................................................................................................................................................................
..............................................................................................................................................................................................................................................
..............................................................................................................................................................................................................................................
..............................................................................................................................................................................................................................................
..............................................................................................................................................................................................................................................
.............................................................................................................................................................................................................................................. [3]

(b) Ammonia is used in the manufacture of fertilisers.

Name the three elements present in most fertilisers which improve plant growth.

1 .......................................................................................................................................................................

2 .......................................................................................................................................................................

3 ....................................................................................................................................................................... [3]

(c) Aqueous ammonia can be used to test for aluminium ions and zinc ions.

Complete the table to show the expected observations.

[Table_1]

$$ \begin{array}{|c|c|c|} \hline \text{ion} & \text{observation on adding a small volume of aqueous ammonia} & \text{observation on adding an excess of aqueous ammonia} \\ \hline \text{aluminium (Al}^{3+}) & & \\ \hline \text{zinc (Zn}^{2+}) & & \\ \hline \end{array} $$ [3]

(a) Magnesium is manufactured by the electrolysis of molten magnesium chloride.

(i) The negative electrode is made of iron.
Suggest a non-metal which could be used for the positive electrode. Give a reason for your answer.

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

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

(b) The following statements are about the procedure for making crystals of hydrated magnesium chloride from magnesium and dilute hydrochloric acid.
A Leave the mixture until no more bubbles are seen.
B Leave the mixture at room temperature to form more crystals.
C Add an excess of magnesium to dilute hydrochloric acid.
D Warm the filtrate to the point of crystallisation.
E Filter off the crystals and dry between filter papers.
F Filter off the excess magnesium.

Put the statements A, B, C, D, E and F in the correct order. The first one has been done for you.
C [ ] [ ] [ ] [ ] [ ] [2]

(c) Magnesium is a metal in Group II of the Periodic Table. Copper is a transition element. Copper has a higher melting point and a higher boiling point than magnesium.

Describe two other properties of copper which are different from those of magnesium.
1 .....................................................................................................................................
2 ..................................................................................................................................... [2]

(d) Chromatography can be used to separate a mixture of ions from different transition element compounds. Four samples, R, S, T and U, each containing transition element ions, were placed on a piece of chromatography paper. Two solutions, Y and Z, each containing only one type of transition element ion were also placed on the same piece of chromatography paper.

The results of the chromatography are shown.


(i) Which sample, R, S, T or U, contains the same ions as both solution Y and solution Z?
..................................................................................................................................... [1]

(ii) Which sample, R, S, T or U, does not contain the same ions as either solution Y or solution Z?
..................................................................................................................................... [1]

(iii) In which sample, R, S, T or U, has the greatest number of transition element ions been separated?
..................................................................................................................................... [1]