SC19b Energy Changes in Reactions

Question 1

what must happen in a chemical reaction? (bonds)

Answer 1

bonds in reactants must break and new bonds are made to form the products

Question 2

endothermic reaction + bonds

Answer 2

energy is taken in by the reactants to break the bonds, so breaking bonds is endothermic

Question 3

exothermic reactions + bonds

Answer 3

energy is given out to the surroundings as bonds form, so making bonds is exothermic

Question 4

when is a reaction exothermic?

Answer 4

when more energy is given out when new bonds are made than is needed to break bonds

Question 5

when is a reaction endothermic?

Answer 5

when more energy is needed to break bonds than is given out when new bonds are made

Question 6

activation energy?

Answer 6

minimum amount of energy needed by colliding particles for a reaction to happen

Question 7

energy profile diagrams?

Answer 7

diagram that shows the amount of activation energy needed in a reaction

Question 8

bond energy?

Answer 8

the energy needed to break one mole of a particular covalent bond

Question 9

particles in one mole?

Answer 9

6.02 x 10²³

Question 10

units for bond energy?

Answer 10

kj mol⁻¹

Question 11

steps to calculating bond energy?

Answer 11

1- calculate energy in (bonds broken)
2- calculate energy out (bonds made)
3- energy change = energy in - energy out

Question 12

if we get a negative number when calculating bond energy what type of reaction is it?

Answer 12

exothermic

Question 13

if we get a positive number when calculating bond energy what type of reaction is it?

Answer 13

endothermic