Topic 5 -Energy changes

Question 1

What is a fuel cell?

Answer 1

An electrical cell supplied with fuel and oxygen which used energy from the reaction to produce electrical energy

Question 2

Explain how a hydrogen-oxygen fuel cell works

Answer 2

The electrolyte is potassium hydroxide
Hydrogen goes in the anode, oxygen in the cathode
At the anode H loses electrons to produce positive ions
The oxygen takes these to produce water - reduction

Question 3

How can fuel cells be used? Give advantages and disadvantages

Answer 3

In vehicles
A - not as many pollutants, rechargeable, store more energy
D - takes space, explosive

Question 4

Bond breaking and forming are exo or endo processes?

Answer 4

Bond breaking - Endothermic. Forming - Exothermic

Question 5

How do you calculate the energy change in a reaction

Answer 5

Find the energy required to break the original bonds. Then find the energy released from forming the new bonds. energy required - energy released = energy change

Question 6

What is an electrolyte?

Answer 6

A liquid containing ions which reacts with the electrodes in a cell.

Question 7

How can you predict the voltage of a cell.

Answer 7

If the metal at electrode A is less reactive than B the voltage is positive and vice versa. Work out which was more reactive (the highest volatage) and the differenct between the two numbers. e.g +0.01

Question 8

Why do non-rechargable batteries lose their charge

Answer 8

The ions in the electrolyte and the metals get used up