Enzymes & Catalysts: True or False?

[parwana]

Which of the following are true about the following reaction ?


O3 + O --> 2 O2



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

b) When Cl is used as a catalyst, it functions as an intermediate in the resulting two-step mechanism

c) The presence of Cl provides a mechanism with lower 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 heterogeneous catalyst


I know for a fact that d is wrong, and i speculate that b is wrong as well. Please help, caus i know ctalysts lower activation energy, but which of these is correct, more than one can be correct.

 

[Borek]

O3 + O --> 2 O2
b) When Cl is used as a catalyst, it functions as an intermediate in the resulting two-step mechanism

Google to check whether it is not the same reaction that is responsible for ozone layer depletion (I am not sure about details but IIRC Cl IS a part of the mechanism). If so, you will have a lot of data to find out correct answers.

 

[parwana]

please help with this conufsing question, i know the catalyst lowers tha activation energy, so shouldn't a and c be right??

 

[GCT]

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

Yes, the catalyst affects the rate of reaction

b) When Cl is used as a catalyst, it functions as an intermediate in the resulting two-step mechanism

I believe this is correct also, catalytic chemical reactions (homogenous) have the first step where the catalyst is consumed and then subsequently reappears at the end step.

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

This seems correct, it lowers the activation energy of the reaction.

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

This seems correct also, I believe it depends on whether or not there are transition states in the reaction. Frequently $\Delta E$, corresponds to the rmodynamic properties and activation energy is a kinetic properties-the rate of reaction. In most cases the two don't correspond.

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

This doesn't seem right.

I'm not quite sure but try finding the environmental chemistry section of your text and browse for PVCs (also in the index of your text). Find the mechanism.