Chemical cells and fuel batteries (5.2)

Question 1

How do cells produce electricity?

Answer 1

Cells contain chemicals which react to produce electricity

Question 2

2 things

The voltage produced by a cell is dependent upon a number of factors including…

Answer 2

the type of electrode and electrolyte

Question 3

How can a simple cell be made?

Answer 3

by connecting two different metals in contact with an electrolyte

Question 4

What are batteries?

Answer 4

(consist of) two or more cells connected together in series

Question 5

What is the benefit of a battery rather than a cell?

Answer 5

provides a greater voltage

Question 6

Why do non-rechargeable cells and batteries stop producing electricity?

Answer 6

In non-rechargeable cells and batteries the chemical reactions stop when one of the reactants has been used up, so there is no flow of electrons so no electricity is produced

Question 7

What is a common example of non-rechargeable batteries

Answer 7

alkaline batteries

Question 8

How can rechargeable and cells batteries be recharged?

Answer 8

because the chemical reactions are reversed when an external electrical current is supplied (e.g. mains supply)

Question 8

How may using more reactive metals change the electricity produced?

Answer 8

The more reactive the metal/element, the greater the voltage (and therefore electricity) produced

Question 8

What are fuel cells supplied by?

Answer 8

an external source of fuel (e.g. hydrogen) and oxygen or air

Question 9

How is the fuel in a fuel cell used to produce electricity?

Answer 9

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

Question 10

What is the overall reaction in a hydrogen fuel cell?

Answer 10

the oxidation of hydrogen to produce water.

Question 11

Hydrogen fuel cells offer a potential (…) to rechargeable cells and batteries

Answer 11

alternative

Question 12

Compare hydrogen fuels cells with rechargeable cells and batteries?

Answer 12

• Hydrogen fuel cells are easier to maintain as there are no moving parts
• Hydrogen fuel cells are smaller/lighter
• Water (harmless) is the only chemical product in hydrogen fuel cells
• Hydrogen fuel cells are more expensive to manufacture
• Hydrogen fuel cells need a constant supply of hydrogen fuel, which is a flammable gas - may cause fire/explosion so more dangerous
• Rechargeable cells/batteries can be recharged many times before being recycled, hydrogen fuel cells do not need recharged and will continue to produce pd as long as fuel is supplied (so better use of resources)

Question 13

What are the half equations at each electrode in a hydrogen fuel cell?

Answer 13

Positive electrode: H₂ → 2H⁺ + 2e⁻

Negative electrode: O₂ + 4H⁺ + 4e⁻ → 2H₂O

Question 14

Why are some fuel cells called alkaline fuel cells?

Answer 14

They contain OH^- ions

which are the ions present in alkaline solutions

Question 15

4 you could give

Give two advantages of using hydrogen fuel cells instead of using rechargeable cells?

Answer 15

• No toxic chemicals to dispose of at the end of the cell’s life
• takes less time to refuel
• travel further before refuelling
• no loss of efficiency

Question 16

Explain the differences between the processes in electrolysis and a chemical cell

Answer 16

Electrolysis - produces electricity

Chemical cell - produces chemical reaction