National 5
Chemistry
Unit 3
Exercise Booklet 1
Chemistry in Society
Adapted from original material by Don Sutherland
Exercise 3.1
1.
(a) Name a metal which reacts with oxygen but does not react with water or dilute acid.
(b) Write both the word equation and the chemical equation for the reaction of the metal
you have chosen with oxygen (assume the metal has a valency of 2 when it forms the
compound).
2.
(a) Name a metal which will react slower than magnesium but faster than iron when it is
added to dilute sulphuric acid.
(b) Write both the word and chemical equations for the metal you have chosen with dilute
sulphuric acid
3.
Two pupils were asked to prepare and collect a sample of hydrogen gas.
Jack said he thought they should do this by reacting magnesium metal with dilute hydrochloric
acid.
Bill said he thought they should do this by reacting sodium metal with dilute hydrochloric acid.
Both methods would work but one is very dangerous to try in school.
By considering the reactions you saw of metals with acid and with water:
(a) State which method you would use to prepare the hydrogen gas.
(b) Explain why you think the other method is dangerous.
Exercise 3.2
1.
Explain what is meant by the term "an ore".
2.
State the names of 3 metals found uncombined in rocks.
3.
State whether these 3 metals are reactive or unreactive.
4.
Explain why the other metals are found in rocks as metal compounds.
5.
Name the 3 common metal compounds which are found in rocks.
6.
Explain the 3 stages necessary to obtain metals from ores.
7.
Name 5 metals which can be obtained from their oxides by heating them with carbon.
8.
Explain what happens to the carbon during the reaction.
Adapted from original material by Don Sutherland
Exercise 3.3
1.
State what else could be used instead of carbon to get the metal from its oxide and what it
changes into during the reaction.
2.
Write a word equation for the reaction of Copper (II) oxide with Carbon.
3.
Change this word equation into a chemical equation (Balance it if you can).
4.
Write a word equation for the reaction of Zinc oxide with Carbon Monoxide.
5.
Change this word equation into a chemical equation.
6.
Name a metal which cannot be obtained by heating its oxide with carbon.
7.
For the metal you have chosen in Q6, state the method that must be used to obtain it.
8.
Explain in terms of the bond strengths in the compounds why metals such as Gold and Copper
were the first to be discovered while metals such as Sodium, Magnesium and Aluminium were
only discovered much later.
Exercise 3.4
1.
(a) State what type of bonding is present in metal oxides.
(b) State the 2 things that must happen to get a metal from a metal oxide.
(c) Using copper from copper oxide as your example, write a ion-electron equation to support
your answer to (b)
(d) Explain why this reaction is called "a reduction"
(e) Explain why carbon and carbon monoxide are called "reducing agents".
2.
(a) Write the word equations to show the 3 reactions taking place in a blast furnace.
(b) Under each word equation, try to write a chemical equation for the reaction.
Adapted from original material by Don Sutherland
Exercise 3.5
1.
It is useful to arrange metals in order of reactivity.
A
Metal A reacts slowly with cold water.
B
Metal B reacts violently with cold water.
C
Metal C does not react with dilute acids.
D
Metal D reacts slowly with dilute acid.
Identify the metal:
(a) that needs to be stored under oil.
(b) which would produce the largest voltage when connected with metal A in a cell.
(c) which can be found in nature as an element.
2.
A young mechanic was told to check the liquid level in a car battery.
(a) (i) What name is given to liquids like this acid in batteries or cells?
(ii) What is the purpose of these liquids in batteries or cells?
(iii) What kind of particles must be present in these liquids?
(b) Car batteries contain acid. Which of the following chemicals serves the same purpose in
a zinc/carbon battery ?
3.
A
zinc
B
carbon
C
solid manganese dioxide
D
ammonium chloride
A pupil filled two test tubes with silver nitrate solution. He placed a coil of copper wire in
tube X and a coil of gold wire in tube Y. The pupil noted a change in tube X but none in
tube Y. (You may wish to refer to the data booklet.)
(a) Explain why a reaction took place in tube X.
(b) Name this kind of reaction.
(c) Using the information in the table below state the changes observed in test tube X.
Species
Colour
Au
golden
Au+
colourless
Cu
copper
Cu2+
blue
Ag
silver
Ag+
colourless
Adapted from original material by Don Sutherland
4.
Zinc can displace copper from a solution of copper (II) nitrate. Show this as
(a) a word equation.
(b) a chemical equation .
5.
A pupil set up the apparatus shown in the diagram below but was unable to obtain a reading
on the meter.
(a) Copy and complete the circuit to show how the pupil could get a reading.
(b) Name the part you have added.
(c) Explain why this part is necessary.
(d) Draw an arrow on your diagram to show the direction of flow of electrons.
6.
Hamish said he thought battery electricity is much better than mains electricity - his mother
disagreed.
State two points in favour of each side of the argument.
7.
We can tell a lot about a metal when we know its position in the electrochemical series or in
a reactivity series.
A
Metal A reacts vigorously with water.
B
Metal B is a liquid at room temperature.
C
Metal C must be stored under oil.
D
Metal D shows no sign of reaction with pure oxygen even when heated to red heat.
E
Metal E is seen to react very slowly with dilute acid at 70oC.
F
Metal F reacts at a steady rate with dilute hydrochloric acid at 20oC.
(a) Identify the metal which would be suitable to prepare a sample of hydrogen in the lab,
using dilute hydrochloric acid.
(b) Identify two metals which:
(i) could be extracted from their oxides by heat alone.
(ii) would need to be extracted from their oxides by heating with carbon.
(iii) could have been among one of the first metals to be discovered.
Adapted from original material by Don Sutherland
Exercise 3.6
1.
Explain what is meant by the term "the electrochemical series".
2.
Explain in terms of their ability to form ions how atoms near the top of the list differ from
those near the bottom of the list.
3.
A cell with copper and magnesium electrodes is thought to give a greater voltage than one
with copper and zinc.
Choose the letters of the two cells which could be used to confirm this:
Adapted from original material by Don Sutherland
4.
The metals below are listed in the same order as they occur in the electrochemical series.
MAGNESIUM
IRON
TIN
COPPER
SILVER
They are connected together in pairs as shown above. The further apart they are in the
electrochemical series, the greater the reading on the meter.
(a) Which of the following combinations will produce the greatest reading?
A
B
C
D
E
P
Copper
Magnesium
Iron
Silver
Tin
Q
Magnesium
Iron
Tin
Copper
Silver
(b) (i) Gold is below silver in the electrochemical series. Would the meter reading in a cell
between gold and magnesium be greater or smaller than the reading between silver
and magnesium?
(ii) Explain your answer.
5.
The following results were obtained from the above experiment.
metal being tested Voltage (V)
Direction of flow of electrons
through the meter
A
1.10
A to copper
B
-0·46
copper to B
C
0·00
—
D
0·80
D to copper
Adapted from original material by Don Sutherland
(a) Which of the metals A, B, C or D is highest in the electrochemical series?
(b) Which of the metals is lower than copper in the electrochemical series?
(c) By mistake copper itself was used as one of the metals. Which one?
(d) The above cell was set up with metal A in place of the copper and metal B as the
metal being tested.
In which direction would the electrons flow?
Look at the Electrochemical Series and answer the following questions in sentences:
6.
(a) Which metal when connected to copper will give the highest voltage reading?
(b) Is this metal close to or far away from copper in the electrochemical series?
7.
(a) Which metal when connected to copper will give the lowest voltage reading?
(b) Is this metal close to or far away from copper in the electrochemical series?
8.
Write a few sentences to explain the position in the electrochemical series of the 2 metals
you would choose if you wished to make a cell to give as large a voltage as possible.
9.
Suggest why silver was given a negative voltage in the results table of your voltages
experiment on Appendix 3.1 when it was connected to copper.
10. State the general rule for the direction of the electron flow when 2 metals are connected up
to make a cell.
11. In which direction will electrons flow in the following:
(a) a magnesium / iron cell.
(b) a silver / aluminium cell
(c) a copper / zinc cell
Adapted from original material by Don Sutherland
Exercise 3.7
Use the displacement rule to write word equations followed by chemical equations (with states) for
each of the following:
(Note: in some cases there may be no reaction; so if this is the case, write the names or chemical
formulae for the reactants, then the arrow, and on the right of the arrow write the words "No
Reaction").
1.
Magnesium added to copper (II) sulphate solution.
2.
Copper added to silver nitrate solution.
3.
Lead added to zinc chloride solution.
4.
Zinc added to iron (II) sulphate solution.
5.
Tin added to magnesium sulphate solution.
Exercise 3.8
1.
(a) Explain the meaning of the term 'oxidation'.
(b) Explain the meaning of the term 'reduction'.
(c) Explain how a 'redox' equation is constructed.
2.
Write a chemical equation and then work out the Redox equation for each of the following
chemical reactions:
Remember to start with a balanced chemical equation each time.
(a) Magnesium added to iron (II) sulphate solution.
(b) Copper added to silver nitrate solution giving silver and copper (II) nitrate solution.
(c) Magnesium added to dilute hydrochloric acid.
(d) Zinc added to dilute nitric acid.
3.
If you look at examples (c) and (d) in 2. you will see that the reaction of a metal with an acid
to make a hydrogen gas is really a displacement reaction.
Hydrogen must therefore be in the electrochemical series.
(a) Discuss with a partner how you might carry out the experiment.
Write a rough plan of the experiment on a sheet of paper and show it to your teacher.
If the plan will work, write it out neatly in your notebook.
(b) Ask your teacher if there is time for you to try the experiment.
If there is time, carry out your experimental plan and write your findings in your notebook,
in the form of a list of metals which will also show the 2 metals between which hydrogen
appears.
If there is not time, consult a Data Booklet and find the necessary information in it. Record
the position of hydrogen in the form of a list of metals which will also show the 2 metals
between which hydrogen appears.
Adapted from original material by Don Sutherland
Exercise 3.9
Collect a copy of the Data booklet and turn to the page for the Electrochemical series.
Remember: There are two things to note about the equations:
A. The equations in the series are all written as reductions.
It is possible to turn any equation into the corresponding oxidation simply by turning it
round and writing it 'backwards' e.g.
Consider the first equation:
Li+(aq)
e−
+
→
Li(s)
This is the reduction
+
e−
This is now the Oxidation
Now turn it round:
Li+(aq)
→
Li(s)
B. Some of the equations do not show metals.
This does not matter. It just shows that other species can also take part in reduction or
oxidation reactions.
1.
(a) Copy and complete the following ion electron equations by putting the electrons in the
correct place.
(b) Beside each equation, state which are oxidation and which are reduction.
2.
(i)
Br2
→
2Br−
(ii)
Mg
→
Mg2+
(iii)
2H+
→
H2
(iv)
Fe2+
→
Fe3+
(v)
2Cl−
→
Cl2
We can use the electrochemical series in Date Books to predict if a reaction will occur. If we
had enough information, we could also predict what you would see when a displacement
reaction occurred.
e.g. The following table gives some information about the colour of some metals and the
colours of their solutions.
Metal
Colour
Colour of solution of metal ions
Copper
Brown solid
Blue liquid
Magnesium
Grey solid
Colourless liquid
Zinc
Grey solid
Colourless liquid
Nickel
Grey solid
Green liquid
Copy the above table.
Collect a copy of the Data Booklet and turn to the electrochemical series.
Adapted from original material by Don Sutherland
Use the series to help you answer the following: (Remember - a metal nearer the top of the list is
more likely to give away electrons and form positive ions than a metal nearer the bottom of the list)
In each of the following, state what you would expect to see and give ion-electron equations to
support your answers.
(a) Magnesium metal added to a solution of nickel (II) ions.
(b) Magnesium metal added to a solution of copper (II) ions.
(c) Zinc metal added to a solution of nickel (II) ions.
3.
A metal X will displace a metal Y from a solution of a nitrate of Y if X is more active than Y.
Here are the results of a series of experiments to illustrate this.
Reactants
zinc + copper nitrate
zinc + silver nitrate
copper + silver nitrate
lead + iron nitrate
lead + copper nitrate
zinc + iron nitrate
silver + lead nitrate
copper + zinc nitrate
iron + lead nitrate
iron + zinc nitrate
Observation
copper forms
silver forms
silver forms
no reaction
copper forms
iron forms
no reaction
no reaction
lead forms
no reaction
(a) From these experiments a pupil concludes that the order of activity of the metals used,
most active first, is:
ZINC
IRON
LEAD
COPPER
SILVER
Explain how this conclusion was arrived at.
(b) Chromium reacts with iron nitrate to form iron.
What ONE other experiment would need to be done to put chromium in its place in the
above activity series?
Adapted from original material by Don Sutherland