Energy Transfer in Reactions

Question 1

What is an exothermic reaction?

Answer 1

An exothermic reaction is one which gives out energy to the surroundings, usually in the form of heat and usually shown by a raise in temp

Question 2

Name 3 exothermic reactions

Answer 2

1) Burning fuels: Combustion
2) Neutralisation reactions
3) Oxidation reactions

Question 3

What are the recants in neutralisation reaction?

Answer 3

Acid and an alkali

Question 4

Give an example of an oxidation reaction

Answer 4

Adding sodium to water produces heat. The sodium emits heats and moves about on the surface of the water as it is oxidised

Question 5

Name 2 everyday uses of exothermic reaction and explain them

Answer 5

1) Hand warmers use exothermic oxidation of iron in air (with a salt solution catalyst) to generate heat.
2) Self-heating cans of drinks rely on exothermic reactions between chemicals and their bases

Question 6

What is an endothermic reaction?

Answer 6

An endothermic reaction is one which takes in energy from the surroundings, usually in the form of heat and usually shown by a fall in temp

Question 7

What is a good example of an endothermic reaction?

Answer 7

Thermal decompositions

Question 8

Heat must be supplied to make calcium carbonate decompose to make [ ].
What’s the symbol equation?

Answer 8

quicklime

CaCO₃ -> CaO + CO₂

Question 9

Name an everyday use of endothermic reactions

Answer 9

Sports injury packs - they take in heat and the pack becomes very cold

Question 10

Describe endo/exo - ness in reversible reactions

Answer 10

If the reaction is endothermic in 1 direction then it will be exothermic in the other direction. The energy absorbed by the endothermic reaction is equal to the energy release during the exothermic reaction

Question 11

What is a good example of a reversible reaction?

Answer 11

Thermal decomposition of hydrated copper sulphate

Question 12

What is he word equation for the thermal decomposition of hydrated copper sulphate?

Answer 12

Hydrated copper sulphate (reversible sign) anhydrous copper sulphate + water

—-> Endothermic

Question 13

Describe the endothermic reaction of the thermal decomposition of hydrated copper sulphate

Answer 13

If you heat blue hydrated copper (II) sulphate crystals it drives the water off and leaves white anhydrous copper (II) sulphate powder. -> Endothermic

Question 14

Describe the exothermic reaction of the thermal decomposition of hydrated copper sulphate

Answer 14

If you then add a couple of drops of water to the white powder (from the endothermic reaction) you get blue crystals again