Chemistry

MINISTRY OF EDUCATION AND HUMAN RESOURCES,
TERTIARY EDUCATION AND SCIENTIFIC RESEARCH

MAURITIUS EXAMINATIONS SYNDICATE
NATIONAL ASSESSMENT AT FORM III
NAME
SCHOOL NAME
CLASS/SECTION
CHEMISTRY OCTOBER 2016

1 hour
Students answer on the Question Paper.
READ THE FOLLOWING INSTRUCTIONS CAREFULLY FIRST
Write your name, the name of your school and your class/section in the spaces provided above.
Write in dark blue or black ink.

You may use a soft pencil for any diagrams, graphs or rough working.
Any rough working should be done in this booklet.
Do not use correction fluid.
There are 7 questions in this paper.

Check that this document consists of 10 printed pages and 2 blank pages.
Any discrepancy in the document must be immediately notified to the responsible officer in your
school.
Answer all questions.
The number of marks is given in brackets [ ] for each question or part question.
The total of the marks for this paper is 50.
©MoE&HR,TE&SR & MES 2016

Question 1 - Multiple Choice (6 marks)
For each item, there is only one correct answer. Draw a circle around the letter which
shows the correct answer.
(a) An example of an element which has a valency of 2 is
A calcium.
B sodium.
C aluminium.
D potassium.
(b) Which one of the following is the correct formula for potassium bromide?
A PBr
B KBr
C KB
D POBr
(c) Polluted air contains toxic gases. An example of a toxic gas is
A N2
B O2
C CO2
D NO2
(d) A piece of blue litmus paper turns red when it is dipped in a solution.
This solution could be
A aqueous ammonia.
B lemon juice.
C lime water.
D aqueous sodium hydroxide.
2
(e) The salt barium sulphate forms a suspension in water. Which one of the following methods
cannot be used to separate it from water?
A Filtration
B Evaporation
C Decantation
D Chromatography
(f) How is the process during which a solid changes into a liquid called?
A condensation
B freezing
C melting
D sublimation
3
©MoE&HR,TE&SR & MES 2016 Please turn over this page
Question 2 (7 marks)
Elements are substances that are made up of only one type of atoms. Elements can be
metallic or non-metallic.
(a) Complete Table 1 by giving one example of a metallic element and one example of a
non-metallic element as well as their symbols.
Element Name Symbol
Metallic ______________________ _______________
Non-metallic ______________________ _______________
Table 1
[2]
(b) All metals are solids at room temperature except __________________ , which is a
liquid. [1]
(c) Carbon burns in air to form carbon dioxide.
(i) What is the valency of carbon in carbon dioxide?
Valency: _________________ [1]
(ii) Write down the balanced chemical equation for the combustion of carbon in excess
air.
_____________________________________________________________ [2]
(iii) The above reaction involves a chemical change.
Give another example of a reaction in everyday life that leads to a chemical

change and the creation of a new product.
_____________________________________________________________ [1]
4
(a) A list of separation methods is given below.
Filtration Chromatography Sublimation

Distillation Using a magnet
Select one suitable method by which each of the following underlined substances can be
separated from the mixture.
Each method can be used only once.
(i) Ammonium chloride from a mixture of calcium chloride and ammonium chloride.
__________________________________ [1]
(ii) Iron filings from a mixture of sand and iron filings.
__________________________________ [1]
(iii) Pure water from sea water.
__________________________________ [1]
(b) Separation techniques are widely used in our everyday life.
Which technique can be used to obtain table salt from sea water in Mauritius?
___________________________________________________________________
___________________________________________________________________ [1]
(c) Water is one of the most important solvents used in everyday life.
(i) Give one solid that readily dissolves in water.
__________________________________ [1]
(ii) Nail polish does not dissolve in water.
Name a common solvent for nail polish.
__________________________________ [1]
5
Ammonium salts can be prepared in the laboratory by a method called titration. The procedure
for preparing an ammonium salt is summarised below, using the set up in Figure 1.
Instructions:
burette
1. Fill the burette with acid A.
clamp 2. Measure 25 cm3 of alkali B
and place it in the conical
acid A flask. Add 2 drops of methyl
orange indicator.
3. Slowly add acid A to the
alkali B until the end point is
reached.
alkali B
Figure 1
(a) Which measuring vessel is used to measure 25 cm 3 of alkali B accurately?
____________________________ [1]
(b) Name acid A and alkali B which can be used in the titration above to prepare ammonium
nitrate solution.
Acid A: _______________________________ [1]
Alkali B: _______________________________ [1]
(c) Write down a balanced chemical equation for the reaction between acid A and alkali B.
__________________________________________________________________ [2]
(d) What type of reaction occurs during titration?
____________________________ [1]
(e) Explain the purpose of the indicator in the reaction and the changes you would observe
during the reaction.
Purpose: __________________________________________________________
__________________________________________________________________
Observation: _______________________________________________________
__________________________________________________________________ [2]
(f) Give one important use of ammonium salts.
__________________________________________________________________ [1]
6
(a) All the gases in Table 2 below are made up of molecules.

Complete the table using (i) as example.
Number of each type of atom

Name of gas Formula
present
(i) Nitrogen N2 2 Nitrogen atoms
_________________________
(ii)
______________________ CO2 _________________________
________________________
(iii) Sulphur trioxide
___________ ________________________
Table 2
[3]
(b) Sulphur dioxide is a pollutant that is released in the air by chemical plants that burn
sulphur.
Sulphur dioxide can also be released in the air by natural events.
(i) Name a natural source of sulphur dioxide.
_______________________________________ [1]
(ii) Sulphur dioxide causes acid rain.

Explain how acid rain is formed.
__________________________________________________________________
__________________________________________________________________
[1]
(iii) Give one way in which acid rain can affect the environment.
__________________________________________________________________
__________________________________________________________________
[1]
7
Copper metal can be extracted from a solution of copper ( II) sulphate by the reaction between
aqueous copper salt and zinc metal. Diagram 1 below shows the reaction process.
(i) Add excess zinc powder
(ii) Stir well solution W

mixture of solids
aqueous filter
copper (II)
sulphate
solution W residue X
filtrate
add dilute sulphuric acid
solution Y
bubbles of gas
solid Z
filter
solution Y
solid Z
Diagram 1
(a) Study the reaction process and answer the following questions:
(i) Write a word equation for the reaction between zinc metal and
copper (II) sulphate solution.
______________________________________________________________ [1]
(ii) Write the balanced chemical equation for the reaction above.
______________________________________________________________ [2]
8
(b) (i) Name the type of reaction that occurs when zinc metal is added to copper (II)
sulphate.
Type of reaction: _______________________________ [1]
(ii) Give another metal that can be used instead of zinc that will lead to a similar
reaction.
Another metal: _______________________________ [1]
(c) (i) Give the name of the gas that is liberated when dilute sulphuric acid is added to
Residue X.
Gas: ______________________________ [1]
(ii) How would you test for this gas in the laboratory?
_______________________________________________________________ [1]
(d) Give the name of
(i) solid Z and its colour;
solid Z: ______________________________
colour: ______________________________
(ii) solution Y: ____________________________
[3]
9
The Earth’s atmosphere is made up of a mixture of different gases.

The pie chart in Figure 2 shows the percentage of different gases present in air.
B: 20%
0.03%
0.97%
A: 79%
Figure 2: Composition of air

(a) Identify gases A and B.
A: _______________________ B: _______________________ [2]
(b) The percentage of carbon dioxide in the atmosphere has increased in the last century
and is a concern for the environment as it increases the greenhouse effect.
(i) Give one possible explanation for the increase of carbon dioxide in the atmosphere.
___________________________________________________________________
___________________________________________________________________
[1]
(ii) Another term for the greenhouse effect is ___________________________ . [1]
(iii) State how the above phenomenon affects our planet in general.
___________________________________________________________________
___________________________________________________________________
[1]
(iv) Give one consequence of the greenhouse effect on Mauritius.
___________________________________________________________________
[1]
10
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MINISTRY OF EDUCATION AND HUMAN RESOURCES,

TERTIARY EDUCATION AND SCIENTIFIC RESEARCH

NATIONAL ASSESSMENT AT FORM III

CHEMISTRY OCTOBER 2016

Students answer on the Question Paper.

READ THE FOLLOWING INSTRUCTIONS CAREFULLY FIRST

Write in dark blue or black ink.

There are 7 questions in this paper.

Answer all questions.

©MoE&HR,TE&SR & MES 2016

(a) An example of an element which has a valency of 2 is

(c) Polluted air contains toxic gases. An example of a toxic gas is

D aqueous sodium hydroxide.

Element Name Symbol

Metallic ______________________ _______________

Non-metallic ______________________ _______________

(c) Carbon burns in air to form carbon dioxide.

(i) What is the valency of carbon in carbon dioxide?

Valency: _________________ [1]

(iii) The above reaction involves a chemical change.

Give another example of a reaction in everyday life that leads to a chemical

(a) A list of separation methods is given below.

Filtration Chromatography Sublimation

(ii) Iron filings from a mixture of sand and iron filings.

(iii) Pure water from sea water.

(b) Separation techniques are widely used in our everyday life.

(i) Give one solid that readily dissolves in water.

(ii) Nail polish does not dissolve in water.

Name a common solvent for nail polish.

Acid A: _______________________________ [1]

Alkali B: _______________________________ [1]

(d) What type of reaction occurs during titration?

(f) Give one important use of ammonium salts.

(a) All the gases in Table 2 below are made up of molecules.

Number of each type of atom

(i) Nitrogen N2 2 Nitrogen atoms

Sulphur dioxide can also be released in the air by natural events.

(i) Name a natural source of sulphur dioxide.

(ii) Sulphur dioxide causes acid rain.

(i) Add excess zinc powder

(ii) Stir well solution W

Type of reaction: _______________________________ [1]

Another metal: _______________________________ [1]

Gas: ______________________________ [1]

(d) Give the name of

(i) solid Z and its colour;

(ii) solution Y: ____________________________

The Earth’s atmosphere is made up of a mixture of different gases.

Figure 2: Composition of air

(ii) Another term for the greenhouse effect is ___________________________ . [1]

(iv) Give one consequence of the greenhouse effect on Mauritius.

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Metallic ________ _

Non-metallic ________ _