ozone depletion

condition necessary

UV light

high temperature

deduce the equation for the formation of the reactive species from CCl4

CCl4 —> CCl3• + •Cl

one of the reactive species formed from CCl4 acts as a catalyst in the decomposition of ozone

two equations to show how this species acts as a catalyst

Cl• + O3 —> ClO• + O2

ClO• + O3 —> Cl• + 2O2

mechanism for the reaction of chlorine with methane

free radical substitution

equation for the mechanism for the reaction of fluorine with fluoromethane (CH3F) to form difluoromethane (CH2F2)

F2 —> 2F•

CH3F + F• —> •CH2F + HF

F2 + •CH2F —> CH2F2 + F•

2•CH2F —> CH2FCH2F

overall equation for the reaction of fluorine with ethane to form CF3CHF2 by this mechanism

CH3CH3 + 5F2 —> CF3CHF2 + 5HF

overall equation for decomposition

2O3 —> 3O2

Equation how nitrogen monoxide catalyses this decomposition

O3 —> O + O2

NO + O3 —> NO2 + O2

O + NO2 —> NO + O2

Mechanism for the reaction of CH3Cl with Cl2 to form CH2Cl2

Cl2 —> 2Cl •

Cl• + CH3Cl —> • CH2Cl + HCl

Cl2 + • CH2Cl —> CH2Cl2 + Cl•

2 • CH2Cl —> CH2ClCH2Cl

name the type of reactive intermediate that acts as a catalyst in this reaction

chlorine free radical

write two equations to show how this intermediate is involved as a catalyst in them decomposition of ozone

Cl • + O3 —> ClO • + O2

ClO • + O3 —> Cl • + 2O2

write an equation for each of the following steps in the mechanism for the reaction of CHF3 with Br2

Br2 —> 2Br •

Br • + CHF3 —> •CF3 + HBr

Br2 + •CF3 —> CBrF3 + Br •

2 •CF3 —> C2F6

2Br • —> Br2

it is more likely for CBrF3 to produce bromine atoms than it is for CCIF3 to produce chlorine atoms

The C-Br bond is weaker than the C-Cl bond

The C-Br bond enthalpy is less than that for C-Cl

write equations to show how bromine atoms act as a catalyst in the decomposition of ozone

Br • + O3 —> BrO • + O2

BrO • + O3 —> Br• + 2O2

how these two decomposition equations show that bromine atoms behave as a catalyst

does not appear in the overall equation

is regenerated