fuel cells

Question 1

fuel cell

Answer 1

an electrical cell that’s supplied with a fuel and oxygen and uses energy from the reaction to produce electrical energy efficiently

Question 2

what happens when a fuel enters a cell?

Answer 2

it becomes oxidised and sets up a potential difference

Question 3

give an example of a fuel cell

Answer 3

hyrdogen-oxygen

Question 4

by-products

Answer 4

water and heat

Question 5

why are fuel cells good for the environment compared to other fuel?

Answer 5

they don’t produce as many pollutants

Question 6

why are fuel cells better than batteries in electric vehicles?

Answer 6

• no toxic chemicals to dispose of at end of life
• take less time to refuel
• travel further before refuelling
• no loss of efficiency

Question 7

what type of reaction is in an hydrogen-oxygen fuel cell?

Answer 7

redox

Question 8

what is different about the electrodes compared to electrolysis?

Answer 8

they are switched-anode is negative

Question 9

where do hydrogen and oxygen go?

Answer 9

hydrogen-anode compartment
oxygen-cathode compartment

Question 10

what happens at the anode?

Answer 10

hydrogen loses electrons to produce H⁺ ions (oxidation)

Question 11

half equation at anode

Answer 11

H₂ -> 2H⁺ + 2e⁻

Question 12

where do H⁺ ions move to?

Answer 12

the cathode

Question 13

what happens at the cathode?

Answer 13

oxygen gains electrons from the cathode and reacts with H⁺ ions (from the acidic electrode) to make water (reduction)

Question 14

half equation at cathode

Answer 14

O₂ + 4H⁺ + 4e⁻ -> 2H₂O

Question 15

what is the electric current?

Answer 15

the electrons flow through an external circuit from the anode to the cathode

Question 16

overall word equation

Answer 16

hydrogen + oxygen -> water

Question 17

overall symbol equation

Answer 17

2H₂ + O₂ -> 2H₂O

Question 18

at which electrode is oxidation, which is reduction?

Answer 18

reduction at cathode, oxidation at anode

Question 19

disadvantages of fuel cells

Answer 19

• hydrogen made from fossil fuels
• hydrogen difficult to store
• hydrogen is flammable
• costs more to refuel

Question 20

what happens in a fuel cell?

Answer 20

hydrogen is oxidised and water is produced

Question 21

why is using a hydrogen-fuel cell seen as non-polluting?

Answer 21

• produces water
• water is not polluting / harmful
• doesn’t produce carbon dioxide

Question 22

what do alkaline fuel cells contain?

Answer 22

OH- ions

Question 23

how do fuel cells produce a potential difference?

Answer 23

the fuel is oxidised electrochemically within the fuel cell to produce a potential difference