Question

What is Hrxn?

Hydroxyl radicals react with and eliminate many atmospheric pollutants. However, the hydroxyl radical does not clean up everything. For example, chlorofluorocarbons, which destroy stratospheric ozone, are not attacked by the hydroxyl radical. Consider the hypothetical reaction by which the hydroxyl radical might react with a chlorofluorocarbon:

OH(g)+CF2Cl2(g)→HOF(g)+CFCl2(g)

Answer 1

Consider,

`OH(g)+CF_2Cl_2(g) to HOF(g)+CFCl_2(g)`

To approximate enthalpies of reaction, we're interested in standard enthalpies of formation for the constituents of the chemical equation. To be sure,

`DeltaH_("rxn")^° = SigmaDeltaH_P^°-SigmaDeltaH_R^°`

Hence,

`DeltaH_"rxn"^° = (1"mol" * (-97.8kJ)/("mol") +1"mol" * (-92.0kJ)/("mol"))`
`- (1"mol" * (39.0kJ)/("mol")+1"mol" * (-491.15kJ)/("mol"))`

`therefore DeltaH_"rxn"^° approx (262.4kJ)/("mol")`

I found the enthalpies of formation here . Some of those constituents are wacky and aren't in most texts.