Fuel cells

Chemical cells and fuel cells produce a voltage.

A student sets up a chemical cell by placing two different metal electrodes, magnesium and iron, into a salt solution.

Figure 3 shows an incomplete diagram of the chemical cell used by the student.

Complete Figure 3 by adding a suitable piece of apparatus to show that a voltage is produced.

Use words from the box to complete labelling of Figure 3.

Describe what happens to the cell's voltage over a long period of time.

One type of fuel cell is the hydrogen‑oxygen fuel cell.

Hydrogen-oxygen fuel cells produce water only.

Write the word equation for the reaction.

Figure 1 shows a chemical cell.

The chemical cell contains two metal electrodes placed into an electrolyte and connected in a circuit with a voltmeter.

State what type of compound must be present in the electrolyte.

When the two metal electrodes are placed in the electrolyte, a voltage is produced.

The bigger the difference in reactivity of the metals, the larger the voltage produced.

Which metal, when used for electrode X in Figure 1, would give the largest voltage?

State what happens to the voltage when one of the reactants is used up.

Hydrogen-oxygen fuel cells can also be used to produce a voltage.

Draw the dot and cross diagram for a molecule of oxygen, O₂.

An atom of oxygen has the electronic configuration of 2.6.

Show outer electrons only.

Hydrogen‑oxygen fuel cells are used in spacecraft.

Suggest one advantage of using fuel cells rather than chemical cells in spacecraft.

Figure 1 shows information about two isotopes of hydrogen, A and B.

Complete the table to show the number of subatomic particles in each isotope.

Hydrogen gas and oxygen gas are used in a hydrogen–oxygen fuel cell.

Separate containers of hydrogen and oxygen are used to supply the gases.

A student tests the voltage supplied by the fuel cell every 15 minutes.

The results are shown in Figure 2.

Describe what Figure 2 shows about how the voltage of this fuel cell varies with time.

A chemical cell is made by placing two electrodes into an aqueous electrolyte.

Figure 3 shows a chemical cell.

State why sodium and sulfur electrodes are not suitable for this experiment.

sodium

sulfur

Chemical cells produce a voltage.

A chemical cell can be made by placing the metals copper and zinc in a beaker of sodium chloride solution.

Figure 1 shows a diagram of this chemical cell.

Describe what will happen to the brightness of the light bulb over a long period of time.

Copper is a transition metal.

Which of the following is most likely to be a property of copper?

A copper atom has a diameter of 0.256 nm.

What is the size of this copper atom in metres?

Brass is an alloy of copper and zinc. One type of brass contains 70% copper.

Zinc atoms are slightly larger than copper atoms.

Draw a labelled diagram in the box to show the arrangement of copper and zinc atoms in this alloy.

Use the circle in the box as a guide to the size of a copper atom.

Hydrogen and oxygen are reactants in some fuel cells.

Which word equation shows the overall reaction that occurs in these fuel cells?

A torch contains a chemical cell. The torch is turned on and then left on for many hours.

Describe what you would see happen when the torch is turned on and then left for many hours.

A chemical cell can be made by placing two metals into an electrolyte.

Figure 3 shows how the voltage of a simple chemical cell can be measured.

A student investigated how the voltage of this cell was affected by the metal used for the rods.

Which is the only variable that should be changed in the investigation?

Explain why covering iron tools with a thin layer of grease prevents rusting.

Sacrificial protection is another way of preventing rusting.

An example of sacrificial protection is when lumps of zinc are connected to the iron-containing structure of an oil rig.

Explain how the zinc protects the iron from rusting.

Hydrogen-oxygen fuel cells, rather than chemical cells, can be used to power some vehicles.

Give one advantage of using a hydrogen-oxygen fuel cell, rather than using a chemical cell, to power a vehicle.

Complete the half-equation for the reaction taking place at one of the electrodes in a hydrogen-oxygen fuel cell.

Calculate the volume of 48 g of oxygen at room temperature and pressure.

(relative atomic mass: O = 16, 1 mol of gas occupies 24 dm³ at room temperature and pressure)

volume of oxygen =_........

*(d) The hydrogen used in a hydrogen-oxygen fuel cell can be produced from methanol, CH₃OH.

In this reaction the forward reaction is endothermic and heat energy is taken in from the surroundings. The conditions used for this reaction are

• a nickel catalyst

• a temperature of 220 °C

Explain, in terms of their effects on the rate of attainment of equilibrium and the equilibrium yield of hydrogen, why the reaction is carried out using a catalyst at 220 °C rather than without a catalyst at a lower temperature.

Methane reacts with steam to form hydrogen and carbon dioxide.

The reaction takes place in two stages.

Stage 1 takes in heat energy, it is endothermic.

Explain the effect of increasing the temperature on the yield of the products of stage 1.

The overall equation for the process is

0.40 g of methane were fully reacted with steam to form carbon dioxide and hydrogen.

Calculate the maximum volume of hydrogen in dm³, measured at room temperature and pressure, that could be made in this reaction.

(relative formula mass: CH₄ = 16, 1 mol of any gas at room temperature and pressure occupies 24 dm³)

*(b) Hydrogen-oxygen fuel cells can be used to provide electrical energy in a spacecraft.

The reaction that takes place in the fuel cell is

hydrogen + oxygenwater

Evaluate the advantages and disadvantages of providing electrical energy in a spacecraft using hydrogen-oxygen fuel cells rather than chemical cells.

In a hydrogen-oxygen fuel cell, hydrogen and oxygen react at the electrodes.

The overall reaction occurring in this fuel cell is a reaction of hydrogen with oxygen.

Write the balanced equation for this reaction.

The electrodes of a fuel cell are in contact with water and air. The electrodes are made of platinum rather than iron.

State why iron is not a suitable metal for the electrodes of the cell.

Platinum acts as a catalyst.

State, in terms of its position in the periodic table, why you would expect platinum to act as a catalyst.

Some metal objects are electroplated.

State two reasons for electroplating a metal object.