FORM 3 CHEMISTRY TIME: 1h 30min

[Pages:9]DIRECTORATE FOR QUALITY AND STANDARDS IN EDUCATION Department of Curriculum Management Educational Assessment Unit

Annual Examinations for Secondary Schools 2016

FORM 3

CHEMISTRY

Track 3

TIME: 1h 30min

Name: ______________________________________

Class: ______________________________________

Useful Data Atomic numbers and relative atomic masses are shown in the periodic table printed on a separate page.

Marks Grid [ For Examiner's use only ]

Question

Section A

Section B

No.

1

2

3

4

5

6

7

8

9

Max

10 10 10 10 10 10 20 20 20

Mark

Actual Mark

Theory Total

Theory Paper: 85%

Practical: 15%

Final Score: 100%

Chemistry ? Form 3 Secondary ? Track 3 ? 2016

Page 1 of 9

SECTION A ? Answer ALL questions. This section carries 60 marks.

1 a) State whether the following statements are True or False:

i) Potassium chloride is a base. ______________

[1]

ii) Anhydrous copper(II) sulfate is white. _____________

[1]

b) Give the electron configuration of:

i) S: ______________

[1]

ii) Al3+: _______________

[1]

c) State which of the following changes are a Physical or a Chemical change:

i) Burning charcoal: _________________

[1]

ii) Melting sulfur: ________________

[1]

d) Write the chemical formula for the following substances:

i) Calcium chloride: ______________

[1]

ii) Magnesium sulfate: _____________

[1]

e) What is the name of the following substances:

i) K2S: ________________________

[1]

ii) Fe(NO3)2: ___________________________

[1]

Page 2 of 9

Chemistry ? Form 3 Secondary ? Track 3 ? 2016

2 The majority of the Earth's atmosphere is made of two gases. One is practically inert while the other supports combustion.

a) What is the name of the gas that is practically inert? How much of this gas does one find in Earth's atmosphere? _____________________________________________________________________ [1]

b) What does the word inert mean? _____________________________________________________________________ [1]

c) What is the name of the gas that supports combustion? How much of this gas exists in the atmosphere? _____________________________________________________________________ [1]

d) Name two other gases that are normally found in clean air. _____________________________________________________________________ [1]

e) In an experiment to find the percentage amount of oxygen in air, copper turnings are heated so that they react with the oxygen present in air. The remaining gas would then be void of oxygen. i) Draw a labelled diagram to show the apparatus used in this experiment.

[3]

ii) State the colour change of the copper turnings during the experiment. ________________________________________________________________ [1]

iii) Write a balanced chemical equation for the reaction between copper and oxygen. Do not include state symbols. ________________________________________________________________ [2]

Chemistry ? Form 3 Secondary ? Track 3 ? 2016

Page 3 of 9

3 The picture shows a kitchen tap that is covered with a layer of deposit due to the hardness found in tap water. This deposit forms over a long period of time and involves a few chemical reactions. The process starts when it rains and ends when water evaporates slowly at the tap.

a) When rain water falls, it mixes and reacts with carbon dioxide in the air. i) What is the name of the substance formed? ________________________________________________________________ [1] ii) Write a balanced chemical equation for the reaction between water and carbon dioxide. Do not include state symbols. ________________________________________________________________ [2]

b) As the acidified rain water is absorbed by the ground, the acidity reacts with the sedimentary rock which in Malta is mostly made of calcium carbonate. The substance formed is soluble and is said to make the water hard. i) What is the name of the soluble substance formed? ________________________________________________________________ [1] ii) What kind of hardness does this substance produce? ________________________________________________________________ [1] iii) Write a balanced chemical equation to show the reaction between calcium carbonate and the acidity in rain. Do not include state symbols. ________________________________________________________________ [2]

c) As we use this hard water through the kitchen tap, some water still remains in the tap after it is closed which evaporates slowly. Over time, this results in a very slow reaction that reforms calcium carbonate on the tap as shown in the picture. Write a balanced chemical equation for this reaction to show how calcium carbonate forms. Do not include state symbols. _____________________________________________________________________ [2]

d) How can the calcium carbonate deposit on the kitchen tap be removed by chemical means? _____________________________________________________________________ _____________________________________________________________________ [1]

Page 4 of 9

Chemistry ? Form 3 Secondary ? Track 3 ? 2016

4 a) Atoms are the building blocks of matter. They are made of sub-atomic particles

called protons, neutrons and electrons. Fill in the following table on the properties of

these sub-atomic particles.

Protons Neutrons Electrons

Mass (a.m.u.)

Charge [3]

b) Sodium fluoride is an ionic compound that is used in toothpaste. It consists of two elements, sodium and fluorine. In nature, fluorine is found as diatomic molecules that are covalently bonded. In the box below, draw a dot cross diagram showing all electron shells, of a molecule of fluorine.

[2] c) State, in terms of electrons, what happens when sodium reacts with fluorine to

produce sodium fluoride. _____________________________________________________________________ [1]

d) Draw a dot cross diagram, showing outer electron shells only, to show the bonding in sodium fluoride.

[2]

e) Chlorine has two isotopes, 1375Cl and 1377Cl. They exist in the ratio of 3:1 respectively. Calculate the relative atomic mass of chlorine. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ [2]

Chemistry ? Form 3 Secondary ? Track 3 ? 2016

Page 5 of 9

5 Acids are a group of compounds that have similar chemical properties.

a) Name two properties of acids. _____________________________________________________________________ [1]

b) What is the range of pH that acids would give when they are dissolved in water? _____________________________________________________________________ [1]

c) What is the difference between a strong and a weak acid? _____________________________________________________________________ _____________________________________________________________________ [1]

d) Hydrochloric acid is a strong mineral acid that reacts with many substances. Name or write formulae of all the substances that will be produced when HCl reacts with: i) Sodium hydroxide, NaOH ________________________________________________________________ [1] ii) Copper oxide, CuO ________________________________________________________________ [1] iii) Magnesium, Mg ________________________________________________________________ [1] iv) Lithium carbonate, LiCO3 ________________________________________________________________ [1]

e) When the kitchen drain becomes clogged with grease, water cannot flow through it properly. Sodium hydroxide can be bought from the hardware store to unclog it. This product comes in concentrated form so that it can eat away at the grease and unclog the blockage easily. Considering the properties of sodium hydroxide, name two necessary precautions when handling this material.

_____________________________________________________________________ _____________________________________________________________________ [1]

f) Write a balanced chemical equation for the reaction between sodium hydroxide and sulfuric acid. Do not include state symbols. _____________________________________________________________________ [2]

Page 6 of 9

Chemistry ? Form 3 Secondary ? Track 3 ? 2016

6 A student was given a task to calculate the ratio of reacting particles in magnesium oxide. To do so, the student was required to burn magnesium ribbon in a crucible as shown in the diagram. a) The student used 0.3 g of clean magnesium. Calculate the number of moles in this amount of magnesium. _____________________________________________________________________ _____________________________________________________________________ [2] b) As the crucible was heated, the student lifted the crucible lid slightly. As she was doing so, the student observed that the magnesium started to glow and so the lid was put back in place so as not to allow any magnesium oxide smoke to escape the crucible. This process was repeated until no more glowing was observed and all of the magnesium reacted. i) Why was the crucible lid opened repeatedly during the experiment? ________________________________________________________________ [1] ii) What was happening when the student observed the magnesium glowing? ________________________________________________________________ [1] iii) Why was it important not to allow smoke to escape the crucible? ________________________________________________________________ [1] c) When the experiment was over and the student reweighed the contents of the crucible, the mass had increased by 0.2 g. This was due to the oxygen that reacted with the magnesium and was equivalent to 0.0125 moles of oxygen. By using your answer in question a) above, calculate the ratio of reacting particles between magnesium and oxygen in magnesium oxide. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ [1] d) Calculate the percentage composition by mass of oxygen in magnesium oxide. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ [2] e) Write a balanced chemical equation for the reaction between magnesium and oxygen. Do not include state symbols. _____________________________________________________________________ [2]

Chemistry ? Form 3 Secondary ? Track 3 ? 2016

Page 7 of 9

SECTION B ? Answer TWO questions only on the foolscaps provided. This section carries 40 marks.

7 A student was given a mixture of three substances; iodine, copper(II) oxide and sodium

chloride. The following table shows the properties of these three substances.

Substance Iodine, I2 Copper(II) oxide, CuO Sodium chloride, NaCl

Solubility in water Insoluble Insoluble Soluble

Colour Bluish black Black Colourless

Action of heat Sublimes Nil Nil

a) This student decided to remove sodium chloride from the rest of the mixture first.

i) Write five sentences to describe how this student could obtain dry sodium

chloride from the rest of the substances.

[5]

ii) Draw two labelled diagrams to show the separating techniques used.

[5]

b) Describe, using a labelled diagram, how the remaining two substances can be

separated from each other.

[8]

c) The student also found two liquid mixtures in the laboratory which needed to be

separated from each other. For each of the mixtures below, choose a separation

technique that would be appropriate in each case.

i) A mixture of water and oil.

[1]

ii) A mixture of water and ethanol.

[1]

8 Oxygen is an important gas that has many uses. It supports combustion and is used by

aerobic organisms to respire. It reacts with most elements. Oxygen is produced on a

large scale by the fractional distillation of liquid air and can also be produced in the

laboratory using several chemical pathways.

a) Name the process by which oxygen is produced industrially.

[1]

b) Write three sentences to outline this industrial process.

[3]

c) Describe in five steps and using a labelled diagram, how oxygen can be produced in

the laboratory using hydrogen peroxide as your starting material and collected over [8]

water.

d) How would you change your setup to produce dry oxygen?

[2]

e) Write a balanced chemical equation for this reaction. Include state symbols.

[3]

f) What type of oxide would be produced when oxygen reacts with:

i) Sulfur

[1]

ii) Magnesium

[1]

iii) Aluminium

[1]

Page 8 of 9

Chemistry ? Form 3 Secondary ? Track 3 ? 2016

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

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download