O LevelChemistryCambridgeTopic Questions4. Electrochemistry4.2 Hydrogen Fuel Cells

Hydrogen Fuel Cells (Cambridge O Level Chemistry)

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1a1 mark
Hydrogen and oxygen react together to form water.

Complete the word equation for this reaction:

hydrogen   +   ____________________   →   water

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1b2 marks

The reaction between hydrogen and oxygen is used in hydrogen fuel cells.

Complete these sentences about hydrogen fuel cells using words from the list.

reduction combustion electricity
     
temperature change gas oxidation


Water is produced when hydrogen undergoes .......................................................

This causes the fuel cell to produce  ..................................................

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1c3 marks

The diagram below shows a hydrogen fuel cell.
aqa-gcse-5-2e-tq3c-hydrogen-fuel-cell


Complete the table to show the functions each of the substances perform in a hydrogen fuel cell using words from the list.

electrolyte electrode waste product
     
source of oxygen fuel anode

Substance Function
Potassium hydroxide solution  
Hydrogen  
Water  

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1d2 marks

Give two advantages of using hydrogen fuel cells compared with using petrol engines to power motor vehicles.

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2a1 mark

The diagram below shows a fuel cell.

fuel-cell

Hydrogen can be used as the fuel.

Complete the balanced symbol equation for the reaction that occurs in a hydrogen fuel cell.

___ H2   +   O2   →   ___ H2O

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2b1 mark

The graph below shows the reaction pathway diagram for the reaction of hydrogen and water in a hydrogen fuel cell.

reaction-profile-v-to-z

Which of the labels represents hydrogen and oxygen? 

Tick one box.

V  
   
W  
   
X  
   
Y  
   
Z  

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2c1 mark

Which of the labels in the reaction pathway diagram in part (b) represents water? 

Tick one box.

V  
   
W  
   
X  
   
Y  
   
Z  

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2d2 marks

The first vehicle powered by a hydrogen fuel cell was built in 1966 by General Motors. It could travel at up to 70 mph in 30 seconds. 

Suggest two disadvantages of using a hydrogen fuel cell in a car.

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1a1 mark

A fuel cell produces electrical energy by the oxidation of a fuel by oxygen.
The fuel is usually hydrogen but methane and methanol are two other fuels which may be used.
A diagram of a hydrogen fuel cell is given below in Figure 1.

hydrogen-fuel-cell

Figure 1

When the fuel is hydrogen, the hydrogen is oxidised to form water, which is the only product.

Suggest what additional product would be formed if methanol was used.

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1b1 mark

Give the chemical equation for the reaction that takes place in a hydrogen fuel cell.

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1c2 marks

In a hydrogen fuel cell, hydrogen loses electrons at the anode.

Write the half equation to show the reaction at the anode.

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1d
Sme Calculator3 marks

Hydrogen and oxygen can also react in a combustion reaction forming water vapour.

Calculate the mass of water vapour produced when 500 cm3 of hydrogen combusts in excess oxygen.


Mass of water vapour ...................................... (g)

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2a3 marks

The Gemini and Apollo moon probes use hydrogen fuel cells to generate an electric current and do not need to be electrically recharged. The product of this reaction can be used to supplement the drinking water for astronauts.

Deduce the half equations for the reactions at each electrode in a hydrogen fuel cell, and then the overall equation for the hydrogen-oxygen fuel cell, to show the product used to supplement drinking water.

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2b1 mark

A hydrogen fuel cell is an electrochemical device that converts chemical energy into electrical energy. A continuous supply of fuel is supplied to one electrode and a continuous supply of air is supplied to the other electrode.

Suggest why a fuel cell does not need to be recharged.

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2c2 marks

The General Motors Electrovan was built in 1966. It was the first vehicle powered by a hydrogen fuel cell and could travel at up to 70 mph for 30 seconds.

Suggest two environmental advantages of using a hydrogen fuel cell rather than an internal combustion engine.

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2d1 mark

Hydrogen fuel cells are commonly considered to be carbon neutral by the general public because they do not release any carbon dioxide or other greenhouse gases when they are used. This is not technically correct.

Suggest why hydrogen fuel cells cannot be classed as carbon neutral.

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1a1 mark

A fuel cell produces electrical energy by the oxidation of a fuel by oxygen.
The fuel is usually hydrogen but methane and methanol are two other fuels which may be used.
A diagram of a hydrogen fuel cell is given below.

hydrogen-fuel-cell

When the fuel is hydrogen, the only product is water.

What additional product would be formed if methane was used?

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1b1 mark

Write the equation for the chemical reaction that takes place in a hydrogen fuel cell.

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1c2 marks

Fuel cells are used to propel cars.

Give two advantages of a fuel cell over a gasoline-fuelled engine.

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2a2 marks

Some cars use hydrogen–oxygen fuel cells as a source of energy.

Explain one advantage to the environment of using a hydrogen–oxygen fuel cell instead of a petrol engine.

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2b1 mark

Fuel cells can be used with alternative fuels. One alternative fuel is the liquid fuel, methanol, CH3OH.


Suggest an advantage of using methanol instead of hydrogen in a fuel cell to power vehicles.

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2c4 marks

When methanol reacts with oxygen in a methanol-oxygen fuel cell, carbon dioxide and water are produced. Draw the reaction pathway diagram for the reaction on the axes below.

Label the following:

  • reactants
  • products
  • activation energy
  • overall energy change

2-4m-q2c-reaction-pathway-diagram

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2d2 marks

Write the balanced symbol equation for the reaction between methanol and oxygen in a methanol-oxygen fuel cell.

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