Which of the following are true about these reactions ?

Question

Chlorofluorocarbons (CFC) act as catalysts for the destruction of ozone in the uper atmosphere.
Ultra violet light from the sun breaks carbon-chlorine bonds in CFC's.



CF2Cl2 ---> CF2Cl + Cl



The Cl atom reacts with ozone.



Cl + O3 ---> ClO + O2
ClO + O ---> Cl + O2



The direct reaction is
O3 + O --> 2 O2



Which of the following are true about these reactions ?



a) The direct reaction breaks down O3 at a faster rate than the same reaction where Cl is used as a catalyst

b) While Cl can be used as a catalyst, it will not appear as an intermediate in the resulting two-step mechanism

c) The presence of Cl provides a mechanism with higher Ea's than the direct reaction (in the absence of Cl)

d) DE (reaction energy) is the same whether Cl is present as a catalyst or not

e) When Cl is used as a catalyst it is a homogeneous catalyst

Answer 1

b d and e

Answer 2

a) No
The opposite is correct. A catalyst speeds up the reaction

b) No
The reaction mechanism contains all intermediates.

c) No
The opposite is correct. A catalyst opens a reaction path with lower activation energy and therefore speeds up the rate of reaction

d) Yes
Catalyst never change reaction enthalpy, energy or equilibrium constants. It only changes the activation energy and speed.

e) Yes
Homogeneous catalysis means catalyst is in the same phase (here gas phase) with reactants and products.

Answer 3

The only one I agree with is e) since everything is in the gas phase and hence homogeneous.

Answer 4

d and e