OZ 5- Removing Ozone

Question 1

Give two definitions of a catalyst

Answer 1

1. Speed up rate of reaction without being used up

2. Provide alternative reaction route with lower activation energy

Question 2

Explain the effect of a catalyst on rate of reaction

Answer 2

Catalyst added, alternate route with lower Ea is provided, more particles have E>Ea, more successful collisions, increased rate

Question 3

Why are there 2 humps on enthalpy profile for reaction using homolytic catalysts>

Answer 3

• an intermediate compound is formed- bonds are made and then broken to form products

Question 4

Explain, with reactions, how chlorine radicals cause the depletion of ozone.

Answer 4

Cl radicals, formed from splitting of organochlorine in atms react with ozone

1. Cl. + O3 ClO + O2
2. ClO + O Cl + O2

Question 5

Explain why chlorine is a catalyst in the depletion of ozone.

Answer 5

Cl is regenerated in reactions with ozone. ClO is intermediate compound.

Question 6

Why are chlorine radicals so bad for ozone?

Answer 6

They are regenerated after depleting ozone, so 1 atom can react with millions of ozone molecules

Question 7

What ways other than chlorine radicals contribute to the depletion of the ozone?

Answer 7

• hydroxyl radicals

- nitrogen monoxide

Question 8

Give the general formula for depletion of ozone

Answer 8

1. X + O3 XO + O2
2. XO + O X + O2
   Overall: O3 + O 2O2