OZ.5 Flashcards
Catalysis
Is bond breaking an endothermic or exothermic process?
Endothermic.
Is the enthalpy change of the reaction the same whether is it uncatalyzed or catalyzed?
Yes.
Does catalysts affect the position of equilibrium in a reversible reaction?
No, they affect the rate at which equilibrium is attained but not the composition of the mixture at equilibrium.
What are homogenous catalysts?
Catalysts that are in the same physical state as the reactants.
Why does the enthalpy profile of homogenous catalyzed reactions have two humps?
Homogenous catalysis work by forming an intermediate compound known as a transition state, and the two hump represent the two steps.
What is CFC?
Chlorofluorocarbon.
What are alkanes called when they contain halogen atoms?
Halogenoalkanes.
What happens to halogenoalkanes when they reach the stratosphere?
Radiation breaks up the molecules to give chlorine or bromine radicals.
Why are chlorine and bromine radicals bad in the stratosphere?
They act as a homogenous catalyst for the process that removes ozone. Chlorine is much worse than bromine.
With X representing a radical, what are the steps that represent the destruction of ozone?
X + O3 → XO + O2
XO + O → X + O2
overall: O3 + O → O2 + O2
As well as chlorine and bromine, what other radicals can destroy ozone in the same way?
Hydroxyl radicals, HO and nitrogen monoxide, NO.
Are all radicals highly reactive?
No, for example NO and NO2 are both radicals but they can be prepared and collected like ordinary molecules.
