4.2. Hydrogen–oxygen fuel cells
A subsection of Chemistry, 0620, through 4. Electrochemistry
Listing 10 of 51 questions
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. cathode anode V e– e– H2 H2O O2 When the fuel is hydrogen, the only product is water. What additional product would be formed if methane was used? Write the equation for the chemical reaction that takes place in a hydrogen fuel cell. At which electrode does oxidation occur? Explain your choice. Write an ionic equation for the reaction at this electrode. Fuel cells are used to propel cars. Give two advantages of a fuel cell over a gasoline-fuelled engine.
0620_w14_qp_33
THEORY
2014
Paper 3, Variant 3
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Hydrogen and oxygen react together in a hydrogen fuel cell. A hydrogen fuel cell is shown in the diagram. membrane water hydrogen H2 oxygen O2 V electrolyte Name the process by which oxygen is obtained from air. In a hydrogen fuel cell, the hydrogen molecules are converted into hydrogen ions, H+, according to the ionic half-equation shown. H2 2H+ + 2e– What type of reaction does this ionic half-equation represent? What type of substance reacts by donating hydrogen ions, H+? Write a chemical equation for the overall reaction that occurs in a hydrogen fuel cell. Hydrogen fuel cells are being developed as alternatives to petrol engines in cars. Give one advantage of hydrogen fuel cells compared to petrol engines. Give one disadvantage of hydrogen fuel cells compared to petrol engines. Some fuel cells use ethanol, C2H5OH, instead of hydrogen. Carbondioxide and water are products of the reaction in an ethanol fuel cell. Write a chemical equation for the overall reaction occurring in an ethanol fuel cell. State an environmental problem caused by the release of carbon dioxide into the atmosphere. Name the process by which ethanol can be manufactured from a renewable resource. Name the process occurring when electrical energy is used to break down an ionic compound.
0620_w17_qp_43
THEORY
2017
Paper 4, Variant 3
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Questions Discovered
51