5.3 Bond enthalpies

Question 1

Bond breaking/forming endothermic/exothermic?

Answer 1

Bond formation - exothermic - E released

Bond breaking - endothermic - E required

Question 2

Explain average bond enthalpy

Answer 2

How much energy needed do break a bond

Refer to reactions in gaseous states, so intermolecular bonds can be avoided

Question 3

ΔH reaction formula considering bond enthalpies

Answer 3

ΔH = E(bonds broken) – E(bonds formed)

Question 4

Photon energy equations

Answer 4

h = Planck’s constant 6.26x10^-34

Question 5

Normal reactions of maintaining ozone

Answer 5

Important because absorbs harmful UV radiation, O2 higher E - double bonds, O3 - lower E 1.5 bonds

Everything in gaseous states, Chapman’s cycle (steady state):

Question 6

Explain depletion of ozone

Answer 6

Chlorofluorocarbons and NO_x disrupt the Chapman’s cycle of maintaining zoone - harmful UV radiation passes - genetic mutations + colder (one of the reactions of maintaining ozone - exothermic)