Download Topic 10 Making electricity

Standard Grade Revision
Unit 10
Q1. Pairs of metals are used to produce a cell.
(a)
What is the purpose of the filter paper soaked in sodium chloride solution?
(b)
What is the direction of the electron flow through the wires?
(c)
Give the name of a metal which could replace the nickel and cause the
electrons to flow in the opposite direction.
(d)
Cells are used in calculators and watches.
Give one advantage of a cell compared with mains electricity.
(a) Acts as the electrolyte – a conducting solution used to complete the circuit by allowing
a flow of ions.
(b) Electrons flow from nickel to copper.
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(c) Gold or silver.
(d) Cells allow equipment to be portable and cells not as dangerous as mains.
Unit 10 Revision
Q2. The diagram shows a copper/zinc cell.
(a) In the cell, electricity flows through the wires from the zinc to the copper.
Name the type of charged particle that flows through the wires.
(b) What is the purpose of the ion-bridge?
(c) Eventually the cell would stop producing electricity.
Give a reason for this.
(d) Name a metal which could replace zinc to produce a larger voltage.
You may wish to use page 7 of the data booklet.
(a) Electrons flow through the wires.
(b) Completes the circuit by allowing a flow of ions.
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(c) One of the chemicals in the cell gets used up.
(d) Magnesium.
Unit 10 Revision
Q3. In an alkaline manganese battery the positive electrode is made of a mixture of
manganese dioxide and carbon. The negative electrode is powdered zinc.
The electrodes are in a paste made of potassium hydroxide.
(a) (i) The potassium hydroxide
(a) (i) Suggest why this type of battery is known as an alkaline battery.
(ii) Why is the potassium hydroxide used in the form of a paste and
is an alkali.
(ii) The ions are not free
not as a dry powder?
(b) Car batteries can be recharged.
(i) What type of electrolyte is used in a car battery?
move in a dry powder.
(b) (i) Sulphuric acid.
(ii) Nickel/Cadmium battery.
(ii) Give one example of a battery that can be recharged.
Q4. A simple cell can be made from everyday objects.
(a) From iron to
(a) In which direction do electrons flow through the wires?
(b) What would happen to the voltage if the iron nail was replaced
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with aluminium foil?
You may wish to use page 7 of the data booklet.
copper.
(b) Increase.
Unit 10 Revision.
Q4. Helen set up the cell shown
opposite
The reaction taking place at electrode A is
Fe3+(aq) + e-
 Fe2+(aq)
(a) (i) In which direction do electrons flow.
(ii) What term is used to describe the type of chemical reaction taking place at electrode A?
(b) Iodine forms at electrode B.
(i) What would you see happening around electrode B?
(ii) Write an ion-electron equation for the chemical reaction taking place at electrode B .
You may wish to use the data booklet to help you.
(a) (i) From the iodide solution to the iron(III) solution (from B to A).
(ii) Reduction (gain of electrons)
Standard Grade Chemistry
(b) (i) A blue black colour appears.
(ii) 2I-(aq)
 I2(aq) + 2e-
Unit 10 Revision.
Q5. Roy wanted to show that chemicals can be used to produce an electric current.
(a) (i) To the copper can
and zinc rod. (as shown)
(ii) Ions cannot flow through
the glass but they can
flow through cardboard.
(iii) Reading would fall.
(b) 6.825 g
When the crocodile clips (labelled A and B) were attached to certain parts of the apparatus, the
ammeter gave a reading.
(a) (i) Where should the crocodile clips be attached to complete the circuit?
(ii) Why was no current produced when the porous cardboard container was replaced by a
glass beaker?
(iii) What would happen to the reading on the ammeter if the zinc rod was replaced with a tin
rod in a tin chloride solution?
(b)
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Roy was instructed to make 50 cm3 of a 1 mol/litre solution of copper chloride, CuCl2.
Calculate the mass, in grams, of copper chloride needed.
Unit 10 Revision.
Q6. Copper displaces silver from silver(I) nitrate solution.
Cu(s) + 2Ag+(aq)
+ 2 NO3- (aq)

Cu2+(aq) + 2 NO3-(aq)
+ 2Ag(s)
(a) Rewrite this equation omitting the spectator ions.
(b) Write the ion-electron equation for the oxidation step in the displacement reaction.
(c) Write the ion-electron equation for the reduction step in the displacement reaction.
(a)
Cu(s) + 2Ag+(aq)  Cu2+(aq) + 2Ag(s)
(b)
Cu(s)
(c)
Ag+(aq) + e-
 Cu2+(aq) + 2e Ag(s)
Q7. Pairs of metals can be used to produce a voltage
zinc
copper
magnesium
lead
tin
Filter
paper
soaked in
sodium
chloride
solution.
iron
Identify the metal in the box above which would produce the smallest voltage is used
Standard Grade Chemistry
in place of zinc.
lead
Unit 10 Revision.
Q8.
Sarah set up the circuit shown below.
Solution containing
bromine, Br2(aq)
Solution containing
sulphite, SO32- ions
In beaker B sulphite ions are converted to sulphate ions.
SO32-(aq) + H2O(l) 
SO42-(aq) + 2H+(aq)
+ 2 e–
(a) In which direction do the electrons flow through the ammeter?
(b) (i) What term is used to describe the type of chemical reaction taking place in beaker B?
( ii) Suggest what would happen to the pH in beaker B.
(c) Write the ion-electron equation for the chemical reaction taking place in beaker A.
You may wish to use the data booklet to help you.
(a) From the sulphite in beaker B to the bromine solution in beaker A.
(b) (i) Oxidation (loss of electrons).
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(ii) pH will fall as hydrogen ions are being produced making the solution acidic.
(c) Br2(a) + 2e-  2Br - (aq)
Unit 10 Revision.
Q9. The diagram shows a cell which can produce electricity.
voltmeter
V
magnesium
tin
solution containing
solution containing
magnesium ions
tin ions
(a) What is the purpose of the ion-bridge?
(a) Completes the circuit.
(b) Name a tin compound which could be used to make the solution
(b) Tin chloride or other
containing tin ions.
(c) In which direction do electrons flow in this cell?
(c) From magnesium to tin
(d) Which electrode will decrease in mass when the cell is operating?
(d) Magnesium
(e) The magnesium electrode undergoes oxidation in this cell.
(e) Mg  Mg2+ + 2e-
Write an ion-electron equation for the oxidation reaction.
(f) Name a metal and a solution which could replace the tin and the
solution containing tin ions which would give a higher voltage than
the cell shown.
Standard Grade Chemistry
soluble tin compound.
(f) Lead or copper , silver
or gold