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

This question is about solids, liquids and gases.
(a) The list gives the names of nine substances.

a aqueous copper(II) sulfate
a aqueous potassium manganate(VII)
a aqueous sodium chloride
a dilute hydrochloric acid
a ethanol
a hexene
a mercury
a octane
a water

Answer the following questions about these substances. Each substance may be used once, more than once or not at all.

State which substance:

(i) is an alkane
.............................................................................................................. [1]
(ii) is used, when acidified, to test for sulfur dioxide
.............................................................................................................. [1]
(iii) turns blue litmus red
.............................................................................................................. [1]
(iv) reacts with sodium to produce only aqueous sodium hydroxide and hydrogen
.............................................................................................................. [1]
(v) is produced by the addition of steam to ethene.
.............................................................................................................. [1]

(b) Some changes of state of mercury 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 motion and separation of the particles in:

liquid mercury ...........................................................................................
..................................................................................................................
..................................................................................................................

mercury gas. ..........................................................................................
.................................................................................................................
.................................................................................................................. [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 | , hydrogen | 1.0, methane | 61.5, nitrogen | 8.5, water vapour | 2.2, other substances | 0.1, total | 100.0]
Deduce the percentage of carbon dioxide present in this sample of biogas.
............................................................................................................................................................. [1]
(b) (i) During the fermentation, carbon dioxide reacts with hydrogen to produce methane and water.
Complete the chemical equation for this reaction.
$$ CO_2 + .....H_2 \rightarrow CH_4 + .....H_2O $$ [2]
(ii) Methane and ethane are in the same homologous series.
What is meant by the term homologous series?
............................................................................................................................................................. [2]
(iii) Draw a dot-and-cross diagram to show the electron arrangement in a molecule of methane, $CH_4$. Show outer shell electrons only.
[2]

(c) Helium and hydrogen can both be used to fill balloons.
Suggest one advantage of using helium rather than hydrogen to fill balloons.
............................................................................................................................................................. [1]

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

(i) On the structure shown, draw a circle around a functional group which reacts with aqueous bromine. [1]
(ii) How many different types of atoms are present in compound $C$?
............................................................................................................................................................. [1]

(e) Ethanol is produced by fermentation of a mixture of plant sugars.
Describe how ethanol can be separated from the rest of the fermentation mixture by fractional distillation. In your answer:
• describe how to do the fractional distillation
• explain how ethanol is separated from the rest of the fermentation mixture using fractional distillation.
............................................................................................................................................................. [4]

(a) A student investigated the reaction of calcium carbonate with an excess of dilute hydrochloric acid by measuring the volume of carbon dioxide produced at 10 second intervals.

$$ \text{CaCO}_3 + 2\text{HCl} \rightarrow \text{CaCl}_2 + \text{CO}_2 + \text{H}_2\text{O} $$

The results are shown on the graph.



(i) How long did it take from the start of the experiment to collect 30 cm³ of carbon dioxide?
............................... s [1]

(ii) At which point on the graph, P, Q, R or S, was the rate of reaction fastest?
Use the graph to explain your answer.

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

(iii) When 0.225 g of calcium carbonate is used, 54.0 cm³ of carbon dioxide is formed.
Determine the mass of calcium carbonate needed to form 216 cm³ of carbon dioxide.

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

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

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

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

• Using larger pieces of calcium carbonate.
All other conditions are kept the same.

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

(b) In industry, calcium oxide is made from calcium carbonate by thermal decomposition.

$$ \text{CaCO}_3 \xrightarrow{\text{heat}} \text{CaO} + \text{CO}_2 $$

(i) Why is this described as thermal decomposition?

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

(ii) State one other use of calcium carbonate in industry.

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

(iii) Calcium oxide is used to treat acidic industrial waste.
State the type of chemical reaction that occurs.

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

An isotope of calcium is written as shown. $$^{44}_{20}\text{Ca}$$
(a) (i) Deduce the number of protons, electrons and neutrons in this isotope of calcium.
number of protons .............................................................
number of electrons ..........................................................
number of neutrons .......................................................... [3]
(ii) State one industrial use of radioactive isotopes.
....................................................................................... [1]
(b) Draw the electronic structure of a calcium atom. [2]
(c) The table shows some information about the reaction of four metals with dry air at room temperature and on heating.

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

[Table_1]

element | melting point in °C | boiling point in °C | density of liquid at boiling point in g/cm³ | colour
fluorine | –220 | –188 | 1.51 |
chlorine | –101 | ....................... | 1.56 | light green
bromine | –7 | 59 | 3.12 | red-brown
iodine | 114 | 184 | ....................... | grey-black

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

(ii) Describe the trend in the melting points of the halogens down the group.
................................................................................................................................................ [1]

(iii) Predict the physical state of bromine at –20°C.
................................................................................................................................................ [1]

(iv) Which one of the following is most likely to be the colour of fluorine? Tick one box.
dark green [ ]
light grey-black [ ]
light yellow [ ]
purple [ ]
[1]

(b) Chlorine reacts with an aqueous potassium salt to form iodine and a different potassium salt.

(i) Complete the word equation for this reaction.


chlorine + ....................... → iodine + .......................
....................... .......................
[2]

(ii) When aqueous sodium fluoride is added to chlorine, no reaction occurs.
Explain, using ideas about the reactivity of the halogens, why no reaction occurs.
................................................................................................................................................
................................................................................................................................................
[1]

(iii) State one use of chlorine.
................................................................................................................................................
[1]

(c) Aqueous silver nitrate is used to test for chloride ions and iodide ions.

(i) The solutions are first acidified with dilute nitric acid.
Explain why dilute hydrochloric acid is not used to acidify the solutions.
................................................................................................................................................ [1]

(ii) Complete the table to show the expected observations.

[Table_2]
ion | observations on adding aqueous silver nitrate
chloride \((Cl^-)\) |
iodide \((I^-)\) |
[3]

(d) A compound of chlorine has the formula \(C_6H_4Cl_2\).
Complete the table to calculate the relative molecular mass of \(C_6H_4Cl_2\).
Use your Periodic Table to help you.

[Table_3]
type of atom | number of atoms | relative atomic mass |
carbon | 6 | 12 | 6 × 12 = 72
hydrogen |
chlorine |

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

(a) Aqueous ammonia is alkaline.
(i) Which one of the following pH values could be the pH of aqueous ammonia?
Draw a circle around the correct answer.
pH 1 pH 5 pH 7 pH 9 [1]
(ii) Ammonia has a strong smell. A beaker of aqueous ammonia was placed in front of a class of students. At first, the students at the back of the class could not smell the ammonia. After a few minutes they could smell the ammonia.
Explain these observations using the kinetic particle model.
.......................................................................................................................................
.......................................................................................................................................
.......................................................................................................................................
.......................................................................................................................................
....................................................................................................................................... [3]

(b) Ammonia is used in the manufacture of nitric acid.
(i) Balance the chemical equation for the first step in the process.
\[ 4NH_3 + 5O_2 \rightarrow .. .. .. NO + 6H_2O \] [1]
(ii) The reaction is exothermic.
What is meant by the term \textit{exothermic}?
.......................................................................................................................................
....................................................................................................................................... [1]
(iii) The NO produced in the first step then reacts with oxygen to produce nitrogen dioxide, NO₂.
\[ 2NO + O_2 \rightarrow 2NO_2 \]
How does this equation show that NO is oxidised?
.......................................................................................................................................
....................................................................................................................................... [1]
(iv) Is nitrogen dioxide an acidic oxide or a basic oxide?
Give a reason for your answer.
.......................................................................................................................................
....................................................................................................................................... [1]

(c) Oxides of nitrogen are atmospheric pollutants.
State one adverse effect of oxides of nitrogen on health.
....................................................................................................................................... [1]

(d) Ammonia reacts with nitric acid to form a salt which is present in many fertilisers.
Name the salt formed when ammonia reacts with nitric acid.
....................................................................................................................................... [1]

(a) Concentrated hydrochloric acid is electrolysed using graphite electrodes.
(i) Name the products of this electrolysis at:
the positive electrode ............................................................
the negative electrode ..........................................................
[2]
(ii) Suggest one observation that is made at the negative electrode.
................................................................................
................................................................................
[1]
(b) Dilute hydrochloric acid reacts with zinc.
Complete the word equation for this reaction.

[2]
(c) The following statements are about the procedure for making crystals of hydrated zinc sulfate from zinc and dilute sulfuric acid.
A Warm the mixture until no more bubbles are seen.
B Add excess zinc to dilute sulfuric acid.
C Warm the filtrate to the point of crystallisation.
D Leave the mixture at room temperature to form more crystals.
E Filter off the excess zinc.
F Filter off the crystals and dry between filter papers.
Put the statements A, B, C, D, E and F in the correct order.
The first one has been done for you.
B

[2]
(d) Zinc is a metal.
(i) Describe three physical properties which are characteristic of metals.
1 ..............................................................................
2 ..............................................................................
3 ..............................................................................
[3]
(ii) An alloy of zinc, copper and nickel is used to make coins.
Suggest two reasons why an alloy is used to make coins and not pure copper alone.
1 ..............................................................................
2 ..............................................................................
[2]