This question is about the elements sodium and fluorine and the compound sodium fluoride.
Dilute aqueous sodium fluoride undergoes electrolysis.
Hydrogen is produced at the cathode.
State what is meant by the term electrolysis.
M1 breakdown by (the passage of) electricity(1)
M2 of an ionic compound in molten or aqueous (state) (1)
Write an ionic half-equation for the production of hydrogen at the cathode.
2H++2e(−)→H2
M1 H++e(−) on left hand side(1)
M2 equation fully correct(1)
Hydrogen is used as a fuel in rockets and is also used in hydrogen fuel cells.
Which statements are correct?
1 Both uses produce water vapour.
2 Burning hydrogen produces polluting gases.
3 A fuel cell produces electricity.
1, 2 and 3
1 and 3 only
1 only
2 and 3 only
B
This question is about electricity and chemical reactions.
Aqueous copper(II) sulfate is an electrolyte.
The electrolysis of aqueous copper(II) sulfate using inert electrodes forms:
- copper at the cathode
- oxygen at the anode.
State what is meant by the term electrolyte.
M1 ionic compound
M2 molten and / or aqueous
State what happens to the colour of the aqueous copper(II) sulfate as this electrolysis progresses.
fades / (becomes) colourless
Write an ionic half-equation for the formation of copper at the cathode.
Cu2++2e→Cu
M1 Cu2+ and (any number of) e on left hand side
M2 equation correct
Give the formula of the ion that forms oxygen at the anode.
OH−
The electrolysis of aqueous copper(II) sulfate is repeated using copper electrodes.
State what happens to the anode.
anode dissolves
Spoons can be electroplated with silver.
Name the substances used as:
the anode (positive electrode)
the cathode (negative electrode)
the electrolyte.
M1 silver
M2 spoon
M3 (aqueous or solution) of silver nitrate
State two reasons why spoons are electroplated.
1
2
M1 prevent corrosion
M2 improve appearance
Hydrogen-oxygen fuel cells can be used to produce electricity to power cars. Petrol produces carbon dioxide and carbon monoxide when it powers cars.
State one disadvantage, other than cost, of using hydrogen-oxygen fuel cells to power cars compared to using petrol.
needs high pressure to store hydrogen
Which statement about fuels is correct?
Heat energy is only produced by burning fuels.
Hydrogen is used as a fuel although it is difficult to store.
Methane is a good fuel because it produces only water when burned.
Uranium is burned in air to produce energy.
B