Malvern College
Qingdao
Upper 5th Chemistry Mock Exam
January 2015
Name (English):
…………………………………………
Name (Pinyin):
………………………………………….
School Number:
…………………………
Chemistry Teacher
………………………………….
Date: ……………………………..
Answer all questions
Time allowed: 2 hours
SECTION A
Q1.
Distress flares are used to attract attention in an emergency. The flares contain magnesium,
which burns with a bright, white flame to form magnesium oxide.
(a) The reaction between magnesium and oxygen is exothermic.
What is meant by the term exothermic?
(1)
.................................................................................................................................................
.................................................................................................................................................
(b) The diagram shows the electronic configuration of a magnesium atom.
Put a cross in a box to indicate the diagram that shows the electronic configuration of an
oxygen atom.
(1)
(c) Magnesium ions and oxide ions are formed when magnesium reacts with oxygen.
The diagram shows the electronic configuration and charge of a magnesium ion.
Put a cross in a box to indicate the diagram that shows the electronic configuration and
charge of an oxide ion.
(1)
(d) A major use of magnesium oxide is as a refractory material, which is a material that can
withstand very high temperatures.
Explain, in terms of its structure and bonding, why magnesium oxide has a very high melting
point.
(4)
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(Total for Question = 7 marks)
Q2.
This apparatus can be used to make and collect carbon dioxide.
This is done by adding dilute hydrochloric acid to calcium carbonate.
(a) Give the names of the pieces of apparatus labelled A, B and C.
(3)
A ............................................................................................................................................
B ............................................................................................................................................
C ...........................................................................................................................................
(b) When an excess of carbon dioxide is bubbled through limewater, reaction 1 occurs,
followed by reaction 2.
The equations for these reactions are
reaction 1
Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)
reaction 2
CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq)
Suggest two observations that would be made when excess carbon dioxide is bubbled
through limewater.
(2)
1 ............................................................................................................................................
.............................................................................................................................................
2 ............................................................................................................................................
.............................................................................................................................................
(c) Carbon dioxide is used in some fire extinguishers because it does not support
combustion.
State another property of carbon dioxide that makes it suitable for use in fire extinguishers.
(1)
.............................................................................................................................................
.............................................................................................................................................
(d) Carbon dioxide is slightly soluble in water. The solution formed has a pH of 5.6
Which is the best description of a solution of carbon dioxide in water?
(1)
A
strongly acidic
B
strongly alkaline
C
weakly acidic
D
weakly alkaline
(Total for Question = 7 marks)
Q3.
Rusting occurs when iron is exposed to air and water. During rusting, iron reacts with
oxygen from the air to form an oxide.
Some students set up this apparatus to measure the volume of oxygen in a sample of air.
Each student used an excess of wet iron filings.
At the start of the experiment the reading on the syringe was recorded and the apparatus
was then left for a week until the reaction was completed.
At the end of the experiment the reading on the syringe was recorded again.
(a) The syringes used in one student's experiment are shown below.
Record the syringe readings at the start and at the end of the experiment in the table
below, and calculate the volume of oxygen used up.
(3)
(b) The results of the other students are shown in the table.
(i) Use the results in the table to plot a graph of volume of oxygen used up against
volume of air at start. Draw a straight line of best fit.
(3)
(ii) One of the results is anomalous. Identify this result by circling it on the graph.
(1)
(c) Another group of students did experiments that gave several anomalous results.
The teacher discussed possible errors that could have caused these anomalous results.
Complete the table by choosing words from the following list to show what effect
each error would have on the volume of oxygen used up.
(3)
(d) Use the following results to calculate the percentage of oxygen in air.
Give your answer to one decimal place.
(2)
........................................................... %
(Total for question = 12 marks)
Q4.
Lead can be extracted from lead(II) sulfide, PbS, in two stages.
Stage 1:
Lead(II) sulfide is heated in air. It reacts with oxygen to produce lead(II)
oxide and sulfur dioxide.
Stage 2:
The lead(II) oxide is then heated in a blast furnace with coke.
(a) Write a chemical equation for the reaction in Stage 1.
(2)
..........................................................................................................................................
(b) The equation for the reaction that occurs when lead(II) oxide is heated with coke in a
blast furnace is:
2PbO + C → 2Pb + CO2
(i) State, with a reason, whether PbO is oxidised or reduced in this reaction.
(1)
..........................................................................................................................................
..........................................................................................................................................
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(ii) Calculate the minimum mass, in tonnes, of coke needed to react with 44.6 tonnes of
lead(II) oxide. [1 tonne = 106 g]
(3)
Mass of coke needed = .................................................... tonnes
(c) The molten lead obtained from the blast furnace contains 0.1% silver dissolved as an
impurity.
The silver is removed by:
adding zinc to the mixture of molten lead and silver at 530 °C and removing the
mixture of molten zinc and silver that forms on top of the molten lead
heating the mixture of molten zinc and silver until the zinc boils off as a gas, leaving
almost pure, solid silver behind.
Use the information above to answer the following questions.
(i) What can you deduce about the relative solubility of silver in zinc and in lead?
(1)
..........................................................................................................................................
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(ii) What can you deduce about the melting point of the mixture of zinc and silver?
(1)
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(iii) What can you deduce about the boiling point of zinc compared to that of silver?
Explain your answer.
(2)
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(iv) Suggest why so much trouble is taken to remove such a small amount of silver from
the lead.
(1)
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(Total for Question = 11 marks)
Q5.
Air is a mixture of gases.
The table gives the formulae of three gases and their approximate percentage by volume in a
sample of dry, unpolluted air.
(a) (i) Give the names of the two main gases in the sample of air.
(1)
.............................................................. and ..............................................................
(ii) Give the name of the gas that makes up most of the remaining 0.96% of the air.
(1)
.............................................................................................................................................
(b) State a use for N2
(1)
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(c) Give the name of a gas present in polluted air that causes acid rain.
(1)
.............................................................................................................................................
(d) A student used this apparatus to find the percentage by volume of oxygen in a sample of
air.
She used this method.





place some wet iron wool in the bottom of a test tube
invert the test tube in a beaker containing water
measure the height of the column of air in the test tube
leave the test tube for one week
measure the new height of the column of air
The table shows her results.
(i) Some of the iron turned into rust.
Write a word equation for this reaction.
(2)
.............................................................................................................................................
(ii) Use the student's results to calculate the percentage of oxygen in this sample of air.
(2)
Percentage of oxygen ...........................................................
(e) The student left the apparatus for another week and measured the height of the column
of air again.
From this measurement, how could she tell whether all of the oxygen in the test tube had
been used up in the first week?
(1)
.............................................................................................................................................
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(Total for Question = 9 marks)
Q6.
Bromine, chlorine and iodine are elements in Group 7 of the Periodic Table.
(a) (i) Identify which of these elements has
(2)
the palest colour
........................................................................
the highest melting point
........................................................................
(ii) Give the name of another Group 7 element that is a solid at room temperature.
(1)
.....................................................
(b) When chlorine and hydrogen react together, hydrogen chloride gas forms.
Write a chemical equation for this reaction.
……………………………………………………………………………………………………
(2)
(Total for Question = 5 marks)
Q7.
The reactivity of metals can be studied using displacement reactions. In these reactions,
one metal is added to a solution of a salt of a different metal.
If a displacement reaction occurs, there is a temperature rise.
A student used the following method in a series of experiments.
Pour some metal salt solution into a polystyrene cup supported in a glass beaker and
record the temperature of the solution.
Add a known mass of a metal and stir.
Record the maximum temperature of the mixture.(a) Suggest three variables that should
be kept the same for the student's experiments to be a fair test.
(3)
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(b) The student used a thermometer to measure the temperature rise. The diagrams show
the thermometer readings before and after adding the metal.
Use the diagrams to complete the table.
(3)
(c) The student used copper(II) sulfate solution in all her experiments. She used five different
metals. She did not know the identity of the metal labelled X.
The student did each experiment twice. The table shows her results.
(i) Which of the metals gave the least reliable temperature rise?
Explain your choice.
(2)
Metal
..........................................................................................................................................
Explanation
..........................................................................................................................................
..........................................................................................................................................
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(ii) Identify the most reactive of the metals used.
Explain how the results show that it is the most reactive.
(2)
Metal
..........................................................................................................................................
Explanation
..........................................................................................................................................
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(iii) Why is there no temperature rise when silver is added to copper(II) sulfate solution?
(1)
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(iv) Why do the results make it impossible to decide which of the metals is the least
reactive?
(1)
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(d) A word equation for one of the reactions is
zinc + copper(II) sulfate → copper + zinc sulfate
Write a chemical equation for this reaction.
(1)
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(Total for Question = 13 marks)
Q8.
This question is about the extraction and uses of aluminium.
(a) Aluminium is extracted from aluminium oxide by electrolysis.
What are the electrodes made of?
(2)
Negative electrode: .............................................................................
Positive electrode: .................................................................................
(b) (i) Explain why the operating temperature would need to be very high if pure aluminium
oxide were used as the electrolyte.
(1)
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(ii) Describe how the operating temperature is kept low.
(1)
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(c) The ionic half-equation for the reaction at the negative electrode is
Al3+ + 3e‾ → Al
What type of reaction is occurring at the negative electrode?
Explain your answer.
(2)
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(d) The waste gases escaping from the electrolysis cell contain carbon dioxide.
Describe how the carbon dioxide is formed.
…………………………………………………………………………………………………
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(2)
(e) Aluminium is used to make cans for food and drinks.
State two properties of aluminium that make it suitable for this use.
You should not refer to cost in your answers.
(2)
1..............................................................................................................................................
2...............................................................................................................................................
(Total for Question = 10 marks)
Q9.
Bromine is an element in Group 7 of the Periodic Table.
(a) (i) State the number of outer electrons in an atom of bromine.
(1)
..........................................................................................................................................
(ii) Identify an element in Group 7 that is a solid at room temperature.
(1)
..........................................................................................................................................
(iii) Identify an element in Group 7 that is more reactive than bromine.
(1)
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(b) Bromine is formed by the electrolysis of molten lead(II) bromide.
The diagram shows the apparatus used.
(i) Solid lead(II) bromide contains ions.
Why does solid lead(II) bromide not conduct electricity?
(1)
..........................................................................................................................................
..........................................................................................................................................
(ii) The formula of lead(II) bromide is PbBr2.
During electrolysis, brown fumes of bromine appear at electrode A.
The ionic half-equation for the reaction at electrode A is
Why is this reaction described as oxidation?
(1)
..........................................................................................................................................
..........................................................................................................................................
(iii) Write an ionic half-equation for the reaction at electrode B and describe the
appearance of the product.
(2)
Ionic half-equation
..........................................................................................................................................
Appearance of product
..........................................................................................................................................
(c) Sodium bromate is a compound of sodium, bromine and oxygen.
A sample of sodium bromate contains 2.3 g of sodium, 8.0 g of bromine and 4.8 g of
oxygen.
Calculate the empirical formula of sodium bromate.
(3)
Empirical formula is ...........................................................
(Total for question = 10 marks)
SECTION B
Q1.
Tungsten is a useful metal. It has the chemical symbol W.
(a) One method of extracting tungsten involves heating a tungsten compound (WO3) with
hydrogen.
(i) Suggest the chemical name of WO3
(1)
.............................................................................................................................................
(ii) Balance the equation for the reaction between WO3 and hydrogen.
(1)
WO3 + ............................H2 → ............................W + ............................H2O
(iii) Why is this reaction described as reduction?
(1)
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(b) Scheelite is an ore of tungsten.
The main compound in scheelite has the percentage composition by mass Ca = 13.9%, W =
63.9%, O = 22.2%.
Calculate the empirical formula of this compound.
(3)
empirical formula = ...........................................................
(Total for Question = 6 marks)
Q2.
Diamond and graphite are two naturally-occurring forms of carbon.
The diagrams below show the arrangement of the carbon atoms in diamond and in
graphite. The black dots (•) represent carbon atoms.
(a) Name the type of structure in diamond and explain, in terms of its bonding, why
diamond has a high melting point.
(4)
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(b) Explain, in terms of its structure, why graphite can act as a lubricant.
(2)
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(c) The structure of graphite has one feature in common with that of metals. This
feature allows graphite to conduct electricity.
Suggest what this feature is and why it allows graphite to conduct electricity.
(2)
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(d) In 1985, a new form of carbon was discovered. It was called buckminsterfullerene
after the architect Buckminster Fuller, who designed buildings with complex
geometric shapes.
Buckminsterfullerene (C60) has a simple molecular structure containing 60 carbon
atoms per molecule. It looks a little bit like a football.
Suggest why buckminsterfullerene has a much lower melting point than diamond.
(2)
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(Total for question = 10 marks)
Q3.
The melting points of three related compounds are
The boiling point of all these compounds is above 100 °C
(a) Use the grid to draw a bar chart of the melting points.
(2)
(b) Room temperature has been marked on the grid.
Use your bar chart to give the physical state of each acid at room temperature.
(2)
capric acid
..........................................................................................................................................
formic acid
..........................................................................................................................................
palmitic acid
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(Total for Question = 4 marks)
Q4.
The photograph shows an aeroplane that has a rocket motor.
(a) One of the tanks on the aeroplane contains liquid oxygen.
(i) Complete the diagram to show the arrangement of the particles in a liquid.
One particle has been drawn for you.
(2)
(ii) Much more oxygen can be stored in the tank when the oxygen is a liquid rather than
a gas.
Give a reason for this in terms of the arrangement of the particles.
(1)
..........................................................................................................................................
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(b) Magnesium burns in oxygen to form magnesium oxide.
(i) State two observations that can be made when magnesium burns in oxygen.
(2)
..........................................................................................................................................
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(ii) Give the formula of magnesium oxide.
(1)
..........................................................................................................................................
(b) A small amount of magnesium oxide is dissolved in water. When universal indicator is
added to this solution, the indicator turns blue.
(i) What does the observation with the indicator show about magnesium oxide?
(1)
..........................................................................................................................................
(ii) Identify the ion that is responsible for the universal indicator turning blue.
(1)
..........................................................................................................................................
(Total for Question = 8 marks)
Q5.
A teacher added some of the Group 1 elements to separate samples of water.
(a) State two observations that could be made when a small piece of sodium is added to a
large trough containing water.
(2)
1
.................................................................................................................................................
..............................................................................................................................................
2
.................................................................................................................................................
..............................................................................................................................................
(b) In another experiment she added a small piece of a different Group 1 element and noticed
that the reaction was less vigorous.
Which element did she add in this experiment?
(1)
.................................................................................................................
(c) When the Group 1 elements react with water, each of their atoms loses an electron from
its outer shell. For sodium and potassium, these processes can be represented by the
equations
 Na → Na+ + e−
 K → K+ + e−
Explain, by referring to the electronic configurations of sodium and potassium, why
potassium is more reactive than sodium.
(4)
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(Total for Question = 7 marks)