year 11 chemistry time: 2 hours€¦ · chemistry – year 11 – track 3 – 2019 page 1 of 12...

Chemistry – Year 11 – Track 3 – 2019 of 12

DEPARTMENT FOR CURRICULUM,

LIFELONG LEARNING AND EMPLOYABILITY

Directorate for Learning and Assessment Programmes

Educational Assessment Unit

Annual Examinations for Secondary Schools 2019

YEAR 11 CHEMISTRY TIME: 2 hours

Name: ________________________________________ Class: _______________

Useful

Data

Atomic numbers and relative atomic masses are shown in the periodic table printed below.

One mole of any gas occupies 22.4 dm3 at standard temperature (0 °C / 273 K) and pressure

(1 atm. / 760 mmHg / 101.3 kPa).

Faraday constant = 96500 C mol-1 Q = I t

PERIODIC TABLE

Marks Grid [For Examiner’s use only]

Question

No.

Section A Section B

1 2 3 4 5 6 7 8 9 10

Max

Mark 7 10 10 7 10 6 10 20 20 20

Theory

Total

Actual

Mark

Theory Paper: 85% Practical: 15% Final Score: 100%

Track 3

of 12 Chemistry – Year 11 – Track 3 – 2019

Section A: Answer ALL questions in the spaces provided.

This section carries 60 marks.

1) Complete:

a) _________________ is a yellow-green gas that turns damp blue litmus paper

red and then bleaches it to white. (1)

b) When electrons are gained in a reduction reaction, this results in a

_________________ in oxidation number. (1)

c) Rhombic and monoclinic are the terms used to describe ________________ of

sulfur. (1)

d) A ____________________ series is a group of organic compounds with the

same functional group and similar chemical properties. (1)

e) ___________________ is the process by which long-chain hydrocarbons are

broken down into simpler molecules. (1)

f) A solution of ______________________ ____________________ gives a

muddy green precipitate with sodium hydroxide solution and a yellow

precipitate with acidified silver nitrate solution. (1)

g) When heated, ______________________ ______________________

decomposes to give a white powder which is heat stable, water vapour and a

gas which turns limewater milky. It also gives a lilac flame colour in a Bunsen

flame. (1)

Total: 7 marks

2) The following question is about nitrogen dioxide.

a) Nitrogen dioxide can be prepared in the laboratory by gently heating white

lead(II) nitrate powder. Besides nitrogen dioxide, a solid and another gas that

relights a glowing splint are formed. Complete and balance the reaction for this

chemical change:

__ Pb(NO3)2(s) → _________ (__) + __ NO2 (__) + ________ (g) (3)


b) The apparatus used for the experiment mentioned in part (a) is shown below. If

the mixture of gases obtained is cooled, the two gases formed can be separated

since one of the gases is liquefied (liquid A).

i) Suggest one safety precaution when carrying out this experiment.

______________________________________________________________

__________________________________________________________ (1)

ii) From the diagram, identify Liquid A and Gas B.

Liquid A: _________________________________________

Gas B: ___________________________________________ (2)

c) Nitrogen dioxide is a brown gas and is found in equilibrium with colourless

dinitrogen tetroxide. This can be represented as follows:

2NO2 (g) ⇌ N2O4 (g) ∆H = negative

The forward reaction is exothermic (i.e. heat energy is released).

Assuming the above equilibrium is occurring in a closed gas syringe, state

how the colour would change, giving reasons, when:

i) the syringe is heated while the volume is kept constant

• colour change:

__________________________________________________

• reason:

__________________________________________________________

__________________________________________________________

__________________________________________________________

______________________________________________________ (2)


ii) the volume of the gas syringe is decreased to increase pressure

• colour change:

__________________________________________________________

• reason:

__________________________________________________________

__________________________________________________________

__________________________________________________________

______________________________________________________ (2)

Total: 10 marks

3) This question is about ammonia.

In the Haber process, nitrogen and hydrogen form an equilibrium in which

ammonia is produced.

a) Give a balanced chemical equation.

___________________________________________________________ (2)

b) Is nitrogen oxidised or reduced in the process? Explain.

_______________________________________________________________

___________________________________________________________ (2)

c) State the conditions used in the process, including the catalyst.

_______________________________________________________________

___________________________________________________________ (3)

d) Draw a dot cross diagram of an ammonia (NH3) molecule (draw outer electron

shells only).

(3)

Total: 10 marks


4) The following question is about sulfuric acid.

a) The Contact Process is used to produce sulfuric acid on an industrial scale. The

process consists of four steps (chemical reactions) that lead to the production of

concentrated sulfuric acid.

i) The second step involves a reversible reaction in which sulfur dioxide gas,

SO2, is oxidised to sulfur trioxide gas, SO3. Give the name or formula of the

catalyst used in this step.

__________________________________________________________ (1)

ii) State and explain whether the use of a catalyst influences the position of

equilibrium.

_____________________________________________________________

_____________________________________________________________

_________________________________________________________ (2)

b) The table below shows reactions involving sulfuric acid:

A CuO + H2SO4 → CuSO4 + H2O

B CuSO4.5H2O 𝑠𝑢𝑙𝑓𝑢𝑟𝑖𝑐 𝑎𝑐𝑖𝑑 → CuSO4 + 5H2O

C Cu + 2H2SO4 → CuSO4 + 2H2O + SO2

Using the letters, A, B and C show where sulfuric acid is acting as:

i) a dehydrating agent: __________________

ii) an acid: _______________

iii) an oxidizing agent: __________________ (3)

c) In two of the reactions shown in the table above, sulfuric acid must be used in

concentrated form. In the other reaction it may be used in dilute form.

Identify the reaction where sulfuric acid may be used in dilute form.

___________________________________________________________ (1)

Total: 7 marks


5) Two students put a conical flask with sodium thiosulfate solution (Na2S2O3) on the

window sill of the laboratory. The students can clearly see a tree in the school field

through the flask. They add hydrochloric acid to the flask and the following

reaction occurs:

Na2S2O3(aq) + 2HCl(aq) → S(s) + SO2(g) + 2NaCl(aq) + H2O(l)

The mixture becomes cloudy due to the insoluble sulfur that forms and as a result,

after some time, the students can no longer see the tree through the flask.

a) The students repeat the experiment using the exact same quantities of

reactants on three different days. They measure the time taken for the tree to

disappear and obtain the following results:

Exp. Day 1: 120 s Exp. Day 2: 200 s Exp. Day 3: 150 s

Which experiment was done on the hottest day? ____________________ (1)

b) The following week, the students perform the three experiments, under the

same conditions using the same chemicals. However, they use different

concentrations of sodium thiosulfate solution. The results for the time taken for

the tree to disappear are as follows:

Exp. 1: 110 s Exp. 2: 100 s Exp. 3: 150 s

i) Which experiment had the strongest solution? ___________________ (1)

ii) Explain your answer using the Collision Theory.

____________________________________________________________

____________________________________________________________

________________________________________________________ (1)

iii) The strongest solution of Na2S2O3 had a concentration of 2.5 mol dm-3 and

50 cm3 of solution were used. Calculate the number of moles of sodium

thiosulfate that react.

(Assume that the acid is present in excess.)

____________________________________________________________

________________________________________________________ (1)


iv) Calculate the amount in grams of sulfur that precipitates.

____________________________________________________________

____________________________________________________________

________________________________________________________ (2)

v) Calculate the volume of sulfur dioxide gas produced at stp.

____________________________________________________________

____________________________________________________________

________________________________________________________ (2)

vi) The students wanted to confirm that the gas produced was indeed SO2.

Describe a test to identify SO2.

____________________________________________________________

________________________________________________________ (1)

c) The students decided to use the same reaction to investigate the rate of

reaction by measuring the volume of SO2 gas produced with time. They used

50 cm3 of 2.5 mol dm-3 Na2S2O3 solution. They obtained the following graph.

The students repeated the experiment using 50 cm3 of 3.5 mol dm-3 Na2S2O3

solution. On the same graph above, draw a sketch of the pattern you would

expect the students to obtain.

(Assume that the acid is in excess in both experiments and that all the SO2 is

released as a gas.) (1)

Total: 10 marks


6) Two students wanted to determine the reactivity of metals

by investigating the rate of reaction of water at room

temperature with sodium and calcium.

a) Look at the diagram and suggest which metal would be

in test tube A.

________________________________________ (1)

b) Explain your answer above using your knowledge about the position of metals

in the periodic table.

______________________________________________________________

______________________________________________________________

__________________________________________________________ (1)

c) Given that the experiment is repeated using magnesium and calcium:

i) Which of the two will be more reactive?

________________________________________________________ (1)

ii) Explain your answer with respect to their atomic structure.

____________________________________________________________

____________________________________________________________

________________________________________________________ (1)

d) Given that the reaction between sodium and water is as follows:

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)

i) State whether sodium has been oxidised or reduced.

_______________________________________________________ (1)

ii) Give the ionic half equation for sodium in this reaction.

_______________________________________________________ (1)

Total: 6 marks

7) This question is about crude oil and the chemicals obtained from it.

a) Many of the hydrocarbon fractions obtained from crude oil belong to the alkane

group.

i) What is the general formula of alkanes?

_________________________________________________________ (1)


ii) Alkanes have only single bonds in their molecules. Are they saturated or

unsaturated?

_________________________________________________________ (1)

iii) The fourth member of alkanes is butane, C4H10. Draw the structural

formulae for two isomers of this hydrocarbon.

(2)

b) Propane is another useful gas obtained from crude oil. But it can also be

prepared by hydrogenation of propene.

i) Complete the equation below for this reaction, by drawing the structures of

propene and propane.

+ H2 →

(2)

ii) What kind of reaction is this?

________________________________________________________ (1)

iii) Mention ONE use of propane.

________________________________________________________ (1)

c) Consider the following compounds.

CH3CH2CH=CH2 CH3CH2CH2CH2CH2CH3 HC≡CH

A B C

i) Write the compounds A, B and C in order of their boiling points, putting the

one with the lowest boiling point first.

________________________________________________________ (1)

ii) Which of A, B or C is most likely to be a liquid at room temperature and

pressure?

________________________________________________________ (1)

Total: 10 marks


Section B: Answer any TWO questions only on the foolscaps and graph paper

provided. This section carries 40 marks.

8) Lactic acid is a weak acid which can be produced by

the body when it is undergoing hard exercise. It

causes muscle pain known as ‘stitch’.

For every molecule of lactic acid that ionises in water,

one H+ ion is produced.

a)

i) What term is used to describe acids that release one H+ ion per

molecule? (1)

ii) What is the meaning of the term ‘weak acid’? (2)

iii) Give another example of a weak acid. (1)

b) During a practical session a student was asked to prepare a 1 litre standard

solution of concentration 0.5 mol dm-3 using powdered lactic acid.

i) Find the RMM of lactic acid and hence calculate the mass of acid which

should be used to prepare this solution. (2)

ii) Make a list of the apparatus needed for such a preparation (3)

iii) Write the method for the preparation of a standard solution. (5)

iv) Draw a diagram of the flask used in this preparation. (1)

c) The lactic acid solution was then used to find the concentration of a solution of

sodium hydroxide. 25 cm3 NaOH required 20.45 cm3 of the lactic acid solution

for complete neutralisation.

The equation for the neutralisation of lactic acid with NaOH follows:

NaOH + CH3CHOHCOOH → CH3CHOHCOONa + H2O

i) Using the above data, calculate the concentration of the NaOH solution. (3)

ii) Both phenolphthalein and universal indicator change colour when there is a

change in pH. Which one of these indicators would you use for this

experiment? Explain your choice. (2)

Total: 20 marks

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjH9vr3vdLaAhUMGewKHT_SAQ4QjRx6BAgAEAU&url=http://www.daviddarling.info/encyclopedia/L/lactic_acid.html&psig=AOvVaw1bY8froSL_GtC4AdV2F8pf&ust=1524644587623784


9) The following article written by Claire Caruana was published in a local newspaper.

Pollution in Malta continues to be among the worst in Europe, with the island

having the fourth highest levels of particles in the air compared to all Member

States. …

According to the agency, road transport, agriculture, power plants, industries and

households are the biggest emitters of air pollution. Heart disease and stroke are

the most common reasons for premature death attributed to air pollution, followed

by lung disease and lung cancer.

Times of Malta, Oct 16th, 2017

a)

i) Give the name and percentage abundance of the two most common gases

found in air. (2)

ii) Give the name and formula of two gases which are known to cause

atmospheric pollution and eventually acid rain. (2)

b) Carbon dioxide is a gas required by plants, but humans are now producing large

quantities of it and this is causing problems.

i) Name two human activities that are contributing to the increase of CO2 in

air. (2)

ii) Name the effect that excess CO2 levels are having on our planet and give

one consequence of it. (2)

c) Fossil fuels such as diesel (C12H26) are known to cause a lot of pollution.

i) Name the separation technique which is used to obtain diesel oil and other

fractions from crude oil. (1)

ii) Write an equation for the complete combustion of diesel. (2)

iii) Explain why incomplete combustion of diesel can be very dangerous. (2)

iv) Draw a labelled diagram of the laboratory apparatus which could be used to

separate two miscible liquids X and Y which have boiling points 85 °C and

120 °C respectively.

Indicate which of the two liquids would be obtained first. (5)

d) Write two suggestions which you would give to the Maltese people to limit and

reduce pollution. (2)

Total: 20 marks


10) In industry, aluminium is extracted from its ore which is mainly composed of

aluminium oxide. This ore is purified before it is electrolysed.

a) Name the ore from which aluminium is extracted. (1)

b) Explain why cryolite is added during the electrolytic process. (1)

c) Explain why the anodes must be replaced regularly. (1)

d) Write a half equation to show what happens at the:

i) Anode (2)

ii) Cathode (2)

e) Calculate the mass of aluminium produced when a current of 200 A is passed

through the system for 8 hours. (3)

f) Aluminium is found in Period 3 of the Periodic table. It is a metal and conducts

electricity.

i) Explain why metals conduct electricity while most non-metals do not. (2)

ii) Sodium chloride conducts electricity when molten or in solution but not when

solid. State why and explain your answer. (2)

iii) Electrical conductivity is a measure of the extent to which a material is a

conductor of electricity. The following table shows the relative electrical

conductivity of the elements in period 3. Draw a graph of element (x-axis)

against relative electrical conductivity (y-axis). (4)

Element Relative electrical

conductivity

Sodium 0.25

Magnesium 0.41

Aluminium 1.00

Silicon 0.10

Phosphorus 0

Sulfur 0

Chlorine 0

Argon 0

iv) From the graph, name the best conductor and explain its conductivity with

reference to its oxidation state. (2)

Total: 20 marks

year 11 chemistry time: 2 hours€¦ · chemistry – year 11 – track 3 – 2019 page 1 of 12...

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