This set of Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Electrochemistry – Fuel Cells”.
1. A fuel cell is a type of electrochemical cell.
Explanation: Fuel cells are the devices which convert the energy produced during the combustion of fuels (chemical energy) like hydrogen, methane, methanol etc. directly into electrical energy. Hence, a fuel cell is a type of electrochemical cell.
2. Which of the following is used as an electrolyte in an H2-O2 fuel cell?
Explanation: The general design of the H2-O2 fuel cell consists of porous carbon electrodes containing suitable catalysts (generally finely divided platinum and palladium) incorporated in them. Concentrated KOH or NaOH solution is placed between the electrodes to act as the electrolyte.
3. Which of the following can be used as fuel in a fuel cell?
Explanation: Hydrogen is the simplest element. It is also abundantly available in the universe. Hydrogen is high in energy, yet an engine that burns pure hydrogen produces almost no pollution. Hence, it used in a fuel cell.
4. Which of the following is not a fuel cell?
a) PEM cell
b) Direct methanol cell
c) Solid oxide cell
d) Daniell cell
Explanation: Polymer electrolyte membrane (PEM) cell, direct methanol cell and solid oxide cell are all types of fuel cells. Daniell cell is a primary galvanic cell with a copper cathode and a zinc-amalgam anode. Daniell cell is a reversible cell.
5. Which of the following is not produced in an H2-O2 fuel cell?
Explanation: Fuel cells convert the chemical energy of fuel into electricity through combustion. Since combustion is an exothermic reaction, heat is evolved. The overall reaction in an H2-O2 cell is:
2H2 (g) + O2 (g) → 2H2O (l)
Thus, water is also produced.
6. Which of the following is supplied to the cathode of a fuel cell?
Explanation: A fuel cell is composed of an anode, cathode, and an electrolyte membrane. A typical fuel cell works by passing hydrogen through the anode of a fuel cell and oxygen through the cathode.
7. Who invented the first fuel cell?
a) Francis Bacon
b) Thomas Grubb
c) Leonard Niedrach
d) William Grove
Explanation: The first fuel cell was conceived by Sir William Robert Grove in 1839. He mixed hydrogen and oxygen in the presence of an electrolyte and produced electricity and water. The fuel cell he made used similar materials to today’s phosphoric acid fuel cell.
8. What is the maximum theoretical energy efficiency of a fuel cell?
Explanation: E°cell of an H2-O2 fuel cell = 1.23 V and ΔH=-285.8 kJ mol-1
ΔG = -n x F x E°cell = -2 x 96500 x 1.23
= -237390 J mol-1
= -237.390 kJ mol-1
Efficiency = ΔG/ΔH x 100
= -237.390/-285.8 x 100
9. Which of the following statements regarding fuel cells is false?
a) Because of continuous supply, fuel cells never become dead
b) They do not cause pollution
c) Fuel cells have 100% efficiency practically
d) The cost of catalysts needed for the electrode reactions is high
Explanation: Theoretically, the fuel cells are expected to have an efficiency of 100%. However, practically they give efficiency of 60-70%. Still, they are much superior to the thermal power plants in which fuels are burnt to produce heat which then changes water into steam to run the turbine. Such a power plant does not have an efficiency of more than 40%.
10. Which of the following are the common ways to produce H2 gas in a fuel cell?
a) Coal and biomass gasification
b) Electrolysis and absorption
c) Steam reforming and electrolysis
d) Electromagnetism and steam reforming
Explanation: Since hydrogen does not exist as a gas on Earth, it must be separated from other elements. Hydrogen atoms can be separated from water, natural gas molecules or biomass. The two most common ways to produce hydrogen are steam reforming (using high-temperature steam to produce hydrogen from natural gas) and electrolysis (splitting water).
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