4.1- ENDOTHERMIC AND EXOTHERMIC REACTIONS

Question 1

What do most chemical reactions do when they proceed? (hint- energy)

Answer 1

give out or take in energy as they proceed

Question 2

What can you do with the amount of energy involved when a chemical reaction takes place? (4)

Answer 2

measure energy values of fuels

calculate requirements for industrial processes

work out theoretical amount of energy to break bonds + amount of energy released when bonds made

helps predict whether or not reaction will take place

Question 3

What forms can the energy involved in a chemical reaction be in? (3)

Answer 3

light, electrical, or most usually heat

Question 4

What is thermochemistry the study of?

Answer 4

study of heat changes during chemical reactions

Question 5

What happens to chemical bonds when a chemical reaction takes place?

Answer 5

chemical bonds break + new ones formed

Question 6

What must be put in for bonds to break?

Answer 6

energy must be put in

Question 7

What must be given out when bonds formed?

Answer 7

energy must be given out

Question 8

As energy must be put in for bonds to break and energy given out for bonds to be broken, what do most chemical reactions involve?

Answer 8

involve energy change

Question 9

What may the overall energy change in a chemical reaction result in?

Answer 9

energy being given out or taken in

Question 10

What sort of reaction is it when energy has been given out?

Answer 10

reaction is exothermic

Question 11

What sort of reaction is it when energy has been taken in?

Answer 11

reaction is endothermic

Question 12

What do some reactions give out as they proceed?

Answer 12

heat

Question 13

What are reactions that give out heat as they proceed called?

Answer 13

exothermic reactions

Question 14

What is an example of an exothermic reaction?

Answer 14

neutralising an acid with an alkali

Question 15

Where do some reactions take in heat from to keep the reaction going?

Answer 15

heat from surroundings

Question 16

What is an example of an endothermic reaction? (hint- limestone)

Answer 16

breakdown of limestone (calcium carbonate) to lime (calcium oxide) + carbon dioxide

Question 17

What is another example of an endothermic reaction? (hint- copper sulphate)

Answer 17

heating copper sulphate

Question 18

What is the formula for blue copper sulphate crystals?

Answer 18

CuS04.5H20

Question 19

How is the water molecules “with” the copper sulphate in blue copper sulphate crystals?

Answer 19

water molecules bonded to copper sulphate

Question 20

What must be done to make white anhydrous copper sulphate from blue copper sulphate crystals?

Answer 20

bonds must be broken between water molecules and copper sulphate

Question 21

What must be supplied to break the bonds between the water molecules and copper sulphate in blue copper sulphate crystals?

Answer 21

heat energy must be supplied

Question 22

If a reaction is endothermic in one direction, what would it be like in the reverse direction?

Answer 22

exothermic

Question 23

What is the amount of heat given out or taken in during a chemical reaction dependent on?

Answer 23

quantity of reactants

Question 24

What is the energy usually measure in?

Answer 24

kJmol-1

Question 25

What is there a large output of when fuels are burnt?

Answer 25

there’s a large heat output

Question 26

What sort of reaction is it when fuels are burnt and there’s a large heat output?

Answer 26

very exothermic reactions

Question 27

Example of endothermic reactions for cold packs?

Answer 27

NH4N03(s) + (aq) -> NH4N03(aq)