21st Century Chemistry
Structured Question in Topic 3
Metals
Unit 9-12
1.
The table below shows information about four different metals — A, B, C and D.
Metal
Cost
Corrosion Conductivity Strength
resistance
A
Low
Low
Medium
Medium
(a)
(b)
(c)
State
Density
Low
B
High
High
Good
High
High
C
Low
Medium
Medium
High
Medium
D
Medium
Medium
Good
Medium
Medium
Which metal is the most suitable for making
medal;
a gate; and
the metal base of a hot pot?
TWO reasons in each case for your choice.
(9 marks)
2.
Consider the following metals:
Aluminium, tin, copper, lead, zinc and titanium
For each of the tasks listed below, choose ONE metal which is best for accomplishing the
task. Explain your choice in each case.
(a) Making space shuttle
(b) Protecting food can from rusting
(c) Making drinking can
(6 marks)
3.
The figure shows a piece of electrical wire.
(a)
(b)
(c)
(d)
Which metal is the most suitable for making electrical wire?
Suggest two essential properties of that metal which make it suitable for making electrical
wire.
Account for the properties mentioned in (b) in terms of metallic bond.
Explain with equation, if any, what will happen if this wire is put into
(i)
dilute hydrochloric acid; and
(ii) silver nitrate solution.
(8 marks)
4.
The table below lists some information about three metals A, B and C.
Metal
A
B
(a)
(b)
(c)
(d)
(e)
5.
Atomic number
12
Action of heating in
air
Action with dilute
sulphuric acid
Burns with bright
light
Colourless gas
bubbles give off
20
C
----
Burns with brick-red
No observable
flame
change
No observable
Reacts vigorously
change
for a short period of
time and then stops
To which group in the periodic table do A and B belong?
(i)
Write an equation for the reaction between A and dilute sulphuric acid.
(An ionic equation will NOT be accepted for this question.)
(ii) Draw the electronic diagram for the gaseous product formed in (i) above,
showing electrons in the outermost shells ONLY.
Explain why metal B reacts with sulphuric acid for a while and then stops?
Suggest what metal C might be.
Explain, in terms of electronic structure, why metal B is more reactive than metal A.
(8 marks)
Some reactions of four metals A, B, C and D are shown below:
Reaction
(i)
A(s) + HCl(aq) → no reaction
(ii) B(s) + HCl(aq) → steady reaction to give hydrogen
(iii) A(s) + O2(g) → slow reaction when heated
(iv) D(s) + O2 (g)
oxide is formed
(v) B(s) + H2O(g) → slow reaction with steam
(vi) C(s) + H2O(g) → vigorous reaction with steam
(a)
(b)
(c)
6.
(a)
(b)
Arrange the four metals in descending order of reactivity. Explain briefly.
Another metal E reacts with dilute hydrochloric acid to give hydrogen. E also shows the
reaction
B(s) + E2+(aq) → B2+(aq) + E(s)
Where would you place E in the reactivity series among A, B, C and D? Explain briefly.
" meant?
(i)
What does the sign "
(ii) Suggest what D might be.
(9 marks)
For each of the following experiments, state ONE observable change and write a
chemical equation for the reaction involved.
(i)
Magnesium is put into dilute hydrochloric acid.
(ii) Sodium is heated under Bunsen flame.
(iii) Lead(II) oxide is heated with carbon powder.
(iv) Zinc is put into copper(II) sulphate solution.
Explain why the there is no reaction in the following experiments.
(i)
Lead is put into dilute sulphuric acid.
(ii) Calcium oxide is heated with carbon powder.
(iii) Copper is put into magnesium nitrate solution.
(14 marks)
7.
Sodium can be used as a drying agent to remove trace of water in organic solvents. Sodium is
first drawn into a wire and placed in a bottle of organic solvent.
(a)
(b)
(c)
(d)
8.
Explain, with the help of equation, why sodium can be used as a drying agent.
Explain why sodium can be drawn into wire in terms of its structure.
When sodium was drawn into wire, it appears shiny at first but turns grey after exposed
to air. Explain this observation with equation.
Suggest a potential hazard of using this method in drying organic solvent.
(7 marks)
The reactivity of metals can be determined by the reaction between metal and acid.
Five different metals, calcium, tin, zinc, copper and nickel are added to dilute hydrochloric acid
in the following set-up. The gas produced is collected by displacement of water. The height of
gas collected is measured.
The results are shown in the following table.
(a)
(b)
(c)
(d)
(e)
(f)
Metal
calcium
tin
zinc
Height (in cm) of gas collected in 30
seconds
5.5
1
4.5
copper nickel
0
2.5
Write the chemical equation for the reaction between zinc and hydrochloric acid.
Suggest a test for the gas evolved.
Determine the reactivity series in descending order from the result provided.
Explain why the reactivity of sodium cannot be determined by this method.
Explain why it is not suitable to use sulphuric acid in determining the reactivity of metal in
this way.
Two other metals were tested and their results were as follow:
Metal
Metal X
Metal Y
Height (in cm) of gas collected in 30 seconds
5
2
From the result obtained, rewrite the reactivity series and suggest what metals X and Y might
be.
(10 marks)
9.
This following table shows the density of two Group I metals.
Metal
Density (g/cm3)
Li
Rb
0.5
1.53
3
(a)
(b)
10.
Density of water = 1.0 g/cm
(i)
Suggest TWO observable differences when lithium(Li) and rubidium(Rb) are added
into a water trough respectively.
(ii) Account for the differences.
(iii) Write the chemical equation for the reaction between rubidium and water.
Rubidium(Rb) is stored in paraffin oil in a bottle with suitable hazard warning labels.
(i)
Why should rubidium be stored in paraffin oil?
(ii) Draw a hazard warning label that should attach on the bottle containing
rubidium.
(7 marks)
A metal, M reacts with very dilute nitric acid to form solution B and a gas C but has no reaction
with steam. When it is heated with Bunsen flame, it gives a solid D. The solid is orange when it
is hot and yellow when it is cold.
(a) Suggest what M, B, C and D might be.
(b) Suggest a test for gas C.
(c) Write balanced equation(s) for extraction of metal M from its sulphide compound.
(d) (i)
Describe what will be observed when a piece of metal M is added to silver nitrate
solution.
(ii) Write an ionic equation for the reaction.
(10 marks)
11.
The following table shows some information of metal reactivity series.
Metal
Extraction method
Ease of extraction
Difficult
K
Na
Ca
Method A
Mg
Al
Zn
Fe
Pb
Carbon reduction
Cu
Hg
Ag
(a)
(b)
(c)
(d)
(e)
(f)
12.
Heating alone
Ease
Briefly describe the method A used in the extraction of reactive metals.
Write the equation for the carbon reduction used in the extraction of copper from
copper(II) oxide.
(i)
Name another reducing agent that can be used instead of carbon to reduce
copper(II) oxide.
(ii) Write the equation for the reaction.
Write the equation for obtaining silver from its oxide by heating alone.
Explain whether reactions occur in the following cases, state ONE observation, if any.
(i)
Put zinc into silver nitrate solution
(ii) Put copper into magnesium nitrate solution
State the relationship between year of discovery and the ease of extraction for metals.
(10 marks)
The following metals arranges in the order of decreasing reactivity.
Metal a ; metal b ; metal c ; iron ; metal d ; metal e ; metal f
Based on the information given above, answer the following questions.
(a) Which metal is most likely to tarnish rapidly in air? Explain your answer.
(b) Which metal is most likely to be found free in nature? Explain your answer.
(c) Would you expect metal d react with cold water? Explain your answer.
(d) Suggest how metal a can be extracted from its ore.
(e) What would be formed when the oxide of metal d is heated with coke?
(f) Suggest an experiment to show that metal b is more reactive than iron.
(g) Can we store a solution of nitrate of metal c in a container made of metal d?
Explain your answer.
(12 marks)
13. A student performs several experiments to determine the order of reactivity of five metals (A, B,
C, D and E). The results are shown in the table below.
Metal
Experiment
A
B
C
D
E
Reacts
Reacts
No reaction
No reaction No reaction
Reaction with water
vigorously
readily
Reacts very
Reacts
Reacts
No reaction
No reaction
Reaction with steam
slowly
vigorously
readily
React
Reacts
Reaction with dilute
Reacts
No reaction
No reaction
slowly
explosively
hydrochloric acid
readily
Metal E
Metal B
Metal C
Heating metal oxide
No reaction
No reaction
obtained
obtained
obtained
with carbon
Displacement
E displaces metal B from a solution of nitrate of B
reaction
(a) Arrange the metals in order of reactivity, starting with the most reactive one. Explain your
answer briefly.
(b) (i)
Suggest what metal A might be.
(ii) Write a chemical equation for the reaction between metal A and dilute
hydrochloric acid.
(iii) State TWO observations when metal A is heated in air.
(c) (i)
Suggest what metal D might be.
(ii) Write a chemical equation for the reaction between metal D and water.
(iii) Suggest how we can extract metal D from its ore.
(d) (i)
During reaction, C forms C2+ ion. Write a chemical equation for the reaction
between C and steam.
(ii) Draw electron diagrams of the products formed in (i) above, showing the
electrons in the outermost shells only.
(e) Metal B forms an oxide with a chemical formula of B2O.
(i)
Suggest what metal B might be.
(ii) Would there be any reaction between zinc and a solution of nitrate of B? Write an
ionic equation for the reaction, if any.
(18 marks)
14.
The following tables record the results of some reactions of four different metals and their
oxides.
Metal
W
Reactions
X
No
Adding dilute hydrochloric Very dangerous!
observable
Never attempt
acid
change
Adding copper(II) nitrate
solution
Oxide
Reactions
Bubbles given
off
Oxide of W
No
observable
change
Oxide of X
Y
Z
Bubbles
given off
Bubbles
given off
Metal
dissolves,
brown solid
deposits
Metal
dissolves,
brown solid
deposits
Oxide of Y
Oxide of Z
No observable Silvery solid is No observable No observable
change
formed
change
change
Silvery grey
No observable
Heating with
No observable
----solid is formed
change
carbon
change
Arrange the four metals in descending order of reactivity. Explain your answer briefly.
If Z burns in air with a bright light, suggest what metal Z might be and write an equation
for its reaction with dilute hydrochloric acid.
Draw the electronic diagrams of the products formed in (b).
Explain the observation, with the help of equation, when metal W is added into copper(II)
nitrate solution.
Suggest and explain an observable change when metal Y is put into copper(II) nitrate
solution.
(12 marks)
Heating alone
(a)
(b)
(c)
(d)
(e)
15.
The results of a series of displacement reactions are given in the table below.
Salt solution
Lead(II)
Iron(II)
Nitrate of X
Silver nitrate
Metal
nitrate
nitrate
X
---reaction occurs reaction occurs reaction occurs
no observable
no observable
reaction occurs
----change
change
Iron
no observable
reaction occurs
---reaction occurs
change
Silver
no observable no observable no observable
---change
change
change
What is displacement reaction?
List two observable changes when X is put into iron(II) sulphate solution?
Based on the information given above, arrange the metals in descending order of
reactivity. Briefly explain your answer.
Chromium should be placed between X and iron in reactivity series. You are provided with
chromium(III) nitrate solution, describe an experiment to show it.
Write an ionic equation for the reaction between iron and silver nitrate solution.
(10 marks)
Lead
(a)
(b)
(c)
(d)
(e)
16.
(a)
Calculate the number of moles of the following substances.
(i)
1.2 x 1025 sodium atoms
(ii) 22.8 g nitrogen dioxide molecules
(iii) 4.8 x 1023 formula units of copper(II) carbonate
(iv) 13.2 g of hydrated magnesium sulphate, MgSO4･7H2O
(b) Calculate the masses of the following substances.
(i)
2 moles of sodium hydroxide, NaOH
(ii) 1.9 x 1024 ethane molecules, C2H6
(iii) 0.4 moles of hydrated sodium carbonate, Na2CO3•10H2O
(iv) 3.90 x 1022 argon atoms
(Relative atomic masses: H = 1.0; C = 12.0; N = 14.0; O = 16.0; Na = 23.0; Mg = 24.0; S =
32.0; Ar = 40.0;Avogadro constant = 6.02x1023)
(8 marks)
17.
(a)
(b)
In 67.5 g of hydrated aluminium sulphate Al2(SO4)3•6H2O, calculate
(i)
the number of moles of aluminium ions, Al3+;
(ii) the number of moles of water molecules;
(iii) the number of sulphur atoms;
(iv) the number of oxygen atoms; and
(v) the number of ions.
When a metal M is completely changed to its ion, 1.96 g of M give 3.60x1022 electrons.
The atomic mass of M is 65.4.
(i)
What is the number of moles of 1.96 g of M?
(ii) What is the number of moles of electrons given out?
(iii) What is the charge on the ions of M?
(Relative atomic masses: H = 1.0; O = 16.0; Al = 27.0; S = 32.0)
(9 marks)
18.
(a) 2.7 g of a metal M combine with 2.4 g of oxygen to form an oxide with the formula M2O3.
What is the relative atomic mass of M?
(b) A crystalline salt (MSO4•7H2O) is found to contain 51.2 % by mass of water of
crystallization. Calculate
(i)
the formula mass of the hydrated salt; and
(ii) the relative atomic mass of the metal M.
(Relative atomic masses: H = 1.0; O = 16.0; S = 32.0)
(6 marks)
19.
(a) 5.1 g of hydrated calcium chloride (CaCl2•nH2O) gives 5.0 g of water on strong heating.
Find the value of n.
(b) A hydrated salt of copper contains 63.9% by mass of the anhydrous salt. The anhydrous
salt has the following percentage composition by mass: copper 39.8%; sulphur 20.0%;
oxygen 40.2%. Find the empirical formula of the hydrated salt.
(Relative atomic masses: O = 16.0; S = 32.0; Cl = 35.5; Ca = 40.0; Cu = 63.5)
(8 marks)
20.
The following diagram shows the apparatus used in an experiment to determine the formula of
black copper oxide.
Town gas (main constituents are carbon monoxide and hydrogen) is passed over the oxide
before heating. During heating, the colour of copper oxide changes from black to brown. After
some time, heating is stopped, town gas was allowed to pass over the copper until it was cold.
The results are as follow:
Mass of tube
= 25.20 g
Mass of tube and copper oxide
= 27.78 g
Mass of tube and copper formed
= 27.26 g
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
21.
(Relative atomic masses: O = 16.0; Cu = 63.5)
Why is it needed to pass the town gas over the oxide before and after the experiment?
What is the mass of copper oxide used?
What is the mass of copper left?
Write appropriate equations to account for the change.
Calculate the number of moles of copper formed.
Calculate the number of moles of oxygen that combined with copper in the copper oxide.
From the results of (e) and (f), determine the empirical formula of copper oxide.
List TWO potential hazards of this experiment.
(11 marks)
A piece of copper weighed 26.78 g is immersed in nitrate solution of metal X in a beaker. A
silvery deposit of X is formed on the copper surface and the solution gradually turns pale blue.
The beaker was then allowed to stand. X is then washed with distilled water and dried. X
weighs 1.94 g and the remaining copper weighs 26.21 g.
(Relative atomic masses: Cu = 63.5; X = 108)
(a) Explain why the solution gradually turns blue.
(b) Calculate the mass of copper reacted with nitrate of X.
(c) (i)
Explain why the solution is allowed to stand.
(ii) Explain why the solid X should be washed and dried.
(d) What is the number of moles of copper reacted?
(e) What is the number of moles of X formed?
(f) What is the number of moles of X reacted when 3 moles of copper(II) ions are formed.
(g) Write an ionic equation for the above reaction.
(10 marks)
22.
A student tried to extract zinc from zinc oxide. He placed 1 g of zinc oxide and 10 g of carbon
powder in a crucible and heated with a Bunsen flame.
(Relative atomic masses: C = 12.0; O = 16.0; Zn = 65.4)
(a) Draw the experimental set-up for the extraction of zinc oxide.
(b) (i)
Write the equation of the reaction involved.
(ii) Suggest one observation for the reaction.
(c) (i)
Determine which reagent is in excess.
(ii) Calculate the maximum mass of zinc that can be obtained.
(d) In fact, the students only obtained 0.6 g of zinc.
(i)
Calculate the yield of the reaction.
(ii) Suggest one reason why the student cannot get the maximum mass of zinc.
(11 marks)
23.
Explain each of the following:
(a) Aluminium does not react with steam unless when aluminium is washed with mercury(II)
chloride.
(b) Silver nitrate solution cannot be kept in an iron bucket.
(c) Aluminium, rather than copper, is used in making electrical cables.
(d) Zinc can be extracted from its molten ore by electrolysis. Yet in practice, it is usually
extracted by heating its oxide with coke.
(e) Galvanized iron is not used in making food can.
(8 marks)
24.
(a)
The above figure shows a factory which extracts zinc from its ore, zinc blende (ZnS). The flow
diagram below shows how zinc is extracted.
ZnS
Stage I
compound X and acidic
gas Y are formed
Stage II
Zn
In stage I, the ore is heated strongly in air. A yellow compound X is formed which becomes
white when cold. Besides, an acidic gas Y is evolved which is emitted to the surroundings from
the chimney.
(i)
(1) Write a chemical equation for stage I.
(2) Give the names of compound X and gas Y.
(ii) In stage II, X is heated strongly with a black powder Z.
(1) What is Z?
(2) Write a chemical equation for stage II.
(iii) State one use of zinc.
(b) Statues A and B are made of iron mainly. It is found that statue A rusts more quickly than
B.
(i)
Give a reason for this.
(ii) Suggest one method to slow down corrosion.
(9 marks)
25.
Explain briefly how the protection against rusting can be achieved in the following cases.
(a) Underground iron gas pipe is jointed to magnesium.
(b) Cloth hangers are coated with plastic.
(c) Bus stop sign is painted.
(d) Bicycle chain is greased.
(e) Car body is connected to the negative terminal of battery.
(10 marks)
26.
Three test tubes are set up in the diagram shown below:
The
(a)
(b)
(c)
(d)
(e)
27.
tubes are left for three days.
Which tube(s) will rusting occur?
What is the function of anhydrous calcium chloride used in test tube A?
What is the function of oil used in test tube B?
Suggest two conditions needed for rusting.
Draw another set-up to show that the presence of ionic substances can increase the rate
of rusting.
(7 marks)
The rusting of iron is investigated by giving five identical iron nails to different treatments. One
nail is left untreated. All six nails are then left for one week exposed to the air. The results are
given in the table below.
Mass of nail and
Mass of nail and
Nail
Treatment
coating before
coating after exposed
exposed to the air
to the air
A Painting
7.0 g
7.3 g
B Coating with wax
7.0 g
6.5 g
C Nickel-plating
7.0 g
7.0 g
D Galvanizing
7.0 g
7.1 g
E Dipping in salt solution
7.0 g
8.9 g
F Untreated
7.0 g
8.2 g
(a) Explain why the mass of the untreated nail has increased after exposed to air.
(b) Which nail is best protected from rusting? Explain your answer.
(c) Which treatment make the rusting worse than untreated iron nail? Explain your answer.
(d) Explain which case is a mistake made in the weighing of the nail.
(e) Which is meant by the treatment 'galvanizing'?
(f) Bridges are protected from rusting by attaching to blocks of magnesium.
(i)
What is the term used to describe this type of rust prevention?
(ii) Suggest why this method is not used to protect iron nails from rusting?
(10 marks)
28.
Aluminium is the most abundant metal on the Earth.
(a) (i)
Name an aluminium ore.
(ii) Suggest how aluminium can be extracted from its ore.
(b) One of the special properties of aluminium is that it has high corrosion resistance.
(i)
Explain why aluminium has such a high corrosion resistance.
(ii) The corrosion resistance of aluminium can be further improved by a method.
(1) Name this method.
(2) Draw the experimental set-up of this method in laboratory.
(c) The reaction of aluminium and zinc nitrate solution can be represented by the following
equation:
2Al(s) + 3Zn(NO3)2(aq) → 2Al(NO3)3(aq) + 3Zn(s)
(i)
Give TWO observations of the above reaction.
(ii) From the information given, explain why the above reaction is a displacement
reaction.
(iii) If 9 g of aluminium is added into excess zinc nitrate solution, calculate the
maximum amount of zinc obtained.
(Relative atomic masses: N = 14.0; O = 16.0; Al = 27.0; Zn = 65.4)
(14 marks)
29.
You are provided with the following materials.
Silver oxide, iron(III) oxide and carbon powder, Bunsen burner, splint, test tubes, delivery tube
and limewater
Suggest three chemical tests to distinguish silver oxide, iron(III) oxide and carbon powder.
(You are required to give a paragraph-length answer. In this question, 6 marks will be awarded
for chemical knowledge and 3 marks for effective communication.)
(9 marks)
30.
You are provided with the following materials.
3 new iron nails, magnesium ribbon, copper foil, gel solution, rust indicator and 3 Petri dishes
Suggest an experiment with explanations which allows you to arrange the reactivity of
magnesium, iron and copper.
(You are required to give a paragraph-length answer. In this question, 6 marks will be awarded
for chemical knowledge and 3 marks for effective communication.)
(9 marks)
31.
Protective coatings are commonly used for rust prevention. Discuss the underlying principle
involved and describe TWO kinds of protective coating and their limitations, with reference to
specific examples.
(You are required to give a paragraph-length answer. In this question, 6 marks will be awarded
for chemical knowledge and 3 marks for effective communication.)
(9 marks)