Fuel cells

Cells contain chemicals that react to produce electricity.

A student investigated the voltage produced by four different cells.

Figure 3 shows the apparatus.

This is the method used.

1. Measure the voltage produced by the cell using metal A as the metal electrode.

2. Repeat using different metals as the metal electrode.

Table 2 shows the results.

Which substance could be used as the electrolyte in the cell in Figure 3 ?

Tick () one box.

Which metal A, B, C or D was copper?

Give one reason for your answer.

Use Figure 3 and Table 2.

Write the four metals A, B, C and D in order of reactivity.

Use Table 2.

A battery consists of several cells connected together in series.

Each cell has a voltage of 3.6 V.

Calculate the number of cells needed to make a battery of voltage 14.4 V.

Fuel cells can be used to power electric cars.

Complete the sentence.

Choose the answer from the box.

The overall reaction in a hydrogen fuel cell involves the oxidation of

Rechargeable cells can be recharged when an external electrical current is supplied.

Complete the sentence.

When an external electrical current is supplied to a rechargeable cell,

the chemical reaction is.

Hydrazine (N₂H₄) is a compound of nitrogen and hydrogen.

Scientists are researching the use of hydrazine in fuel cells.

Table 2 gives some information about the use of hydrogen and hydrazine in fuel cells.

Evaluate the use of hydrazine instead of hydrogen in a fuel cell.

Figure 6 shows a model of the hydrazine molecule.

Complete the dot and cross diagram for hydrazine in Figure 7.

Show the outer shell electrons only.

Give one advantage of the ball and stick model in Figure 6 compared to the dot and cross diagram.

Figure 8 shows the displayed formula equation for the reaction of hydrazine with oxygen.

The reaction is exothermic.

The energy released forming new bonds is 581 kJ/mol greater than the energy needed to break existing bonds.

Table 3 shows some bond energies.

Calculate the bond energy (X) of the bond.

A student investigated the voltage produced by different pairs of metal electrodes in a chemical cell.

Figure 6 shows the apparatus.

This is the method used.

1. Place a nickel electrode and an electrode made from a different metal (electrode A in 1.0 mol/dm³ sodium chloride solution.

2. Measure the voltage produced.

3. Repeat using different metals for electrode A.

Table 3 shows the results.

Write the symbols of the five metals in Table 3 in order of reactivity.

Justify your answer.

Most reactive Least reactive

The voltage produced by a chemical cell depends on the concentration of the electrolyte solution.

Plan an experiment to investigate how the voltage produced by a chemical cell varies with the concentration of the electrolyte solution.

The following substances are available:

• the metal electrodes in Table 3

• 1.0 mol/dm³ sodium chloride solution

• pure water.

Describe how a hydrogen fuel cell produces a potential difference.

This question is about chemical reactions and energy. Hydrogen reacts with oxygen to produce water. This reaction releases energy.

Complete the word equation for the reaction. [1 mark hydrogen + oxygen → ____________

Figure 3 shows a reaction profile for the reaction between hydrogen and oxygen.

What do the labels W, X, Y and Z represent? Choose answers from the box.

The reaction between hydrogen and oxygen is used in a hydrogen fuel cell. What is the reason for using this reaction in a fuel cell? Tick (✓) one box.

A student investigated the voltage produced by a chemical cell. The student used different metals as the electrodes in the cell. The metals used were:

• copper

• iron

• magnesium.

Which two metal electrodes would produce the greatest voltage when used in the chemical cell? Give one reason for your answer.

The reaction between hydrogen and oxygen releases energy.

A student drew a reaction profile for the reaction between hydrogen and oxygen. Figure 3 shows the student’s reaction profile.

The student made two errors when drawing the reaction profile. Describe the two errors.

The reaction between hydrogen and oxygen in a hydrogen fuel cell is used to produce electricity. Hydrogen fuel cells and rechargeable cells are used to power some cars. Give two advantages of using hydrogen fuel cells instead of using rechargeable cells to power cars.

Reactions occur at the positive electrode and at the negative electrode in a hydrogen fuel cell. Write a half equation for one of these reactions.

The three states of matter can be represented by a simple particle model. Figure 4 shows a simple particle model for hydrogen gas.

Give two limitations of this simple particle model for hydrogen gas.

The hydrogen gas needed to power a car for 400 km would occupy a large volume. Suggest one way that this volume can be reduced.

The energy needed for a car powered by a hydrogen fuel cell to travel 100 km is 58 megajoules (MJ). The energy released when 1 mole of hydrogen gas reacts with oxygen is 290 kJ The volume of 1 mole of a gas at room temperature and pressure is 24 dm³ Calculate the volume of hydrogen gas at room temperature and pressure needed for the car to travel 100 km

This question is about chemical cells. A student investigated the voltage produced by different chemical cells. Figure 9 shows the apparatus.

This is the method used.

1. Use cobalt as electrode X.

2. Record the cell voltage.

3. Repeat steps 1 and 2 using different metals as electrode X.

Suggest two control variables used in this investigation.

Table 4 shows the student’s results.

Write the six metals used for electrode X in order of reactivity. Use Table 4. Justify your order of reactivity.

Which of the following pairs of metals would produce the greatest voltage when used as the electrodes in the cell? Use Table 4. Tick (✓) one box.

Hydrogen fuel cells can be used to power different forms of transport. Some diesel trains are being converted to run on hydrogen fuel cells. A newspaper article referred to the converted trains as the new ‘steam trains’. Suggest why.

Chemical reactions can produce electricity.

Figure 13 shows a simple cell.

Which of these combinations would not give a zero reading on the voltmeter in Figure 13 ?

Tick one box.

Electrode A
Electrode B
Electrolyte

Alkaline batteries are non-rechargeable.

Why do alkaline batteries eventually stop working?

Why can alkaline batteries not be recharged?

Hydrogen fuel cells and rechargeable lithium-ion batteries can be used to power electric cars.

Complete the balanced equation for the overall reaction in a hydrogen fuel cell.

Table 7 shows data about different ways to power electric cars.

Evaluate the use of hydrogen fuel cells compared with rechargeable lithium-ion batteries to power electric cars.

Use Table 7 and your own knowledge.

Chemical reactions can produce electricity.

Figure 2 shows a simple cell.

Which of these combinations would not give a zero reading on the voltmeter in Figure 2 ?

Tick one box. Electrode A Electrode B Electrolyte

Alkaline batteries are non-rechargeable.

Why do alkaline batteries eventually stop working?

Why can alkaline batteries not be recharged?

Hydrogen fuel cells and rechargeable lithium-ion batteries can be used to power electric cars.

Complete the balanced equation for the overall reaction in a hydrogen fuel cell.

Table 1 shows data about different ways to power electric cars.

Evaluate the use of hydrogen fuel cells compared with rechargeable lithium-ion batteries to power electric cars. Use Table 1 and your own knowledge.