Question

Before being phased out by the Montral Protocol in the late 80's, the chlorofluorocarbon CFC-12 (CF₂Cl₂) contributed significantly to the destruction of the ozone layer. In the years before the Montreal Protocol, the concentration of CFC-12 in the atmosphere was 388.3 pptv and it increased by 4.87% per year. The atmospheric lifetime of CFC-12 is 100 years and the volume of the atmosphere is 4.30•10²¹ L at 1.00 atm and 15.0 °C. What was the flow (in kg/year) of CFC-12 into the atmosphere during that time?

Answer 1

The global average mass of CFC-12 is,

Rate of change = Emission rate – Loss rate

dm/dt = E-km

m = atmospheric mass of CFC-12

E = rate of emission

k = 1/t = 1/100 = 0.01 yr^-1

Therefore,

E = (dm/dt)+km

taking m common we get equation,

E =[(dm/mdt)+k]m

substituting in the above equation,

rate of accumulation, (dm/mdt) = 4.87% yr^-1 or 0.0487 yr^-1

atmospheric mass of CFC-12 = m = M_CFCC_CFCN_A = = 0.118 x 388.3 x10^-12 x 1.8x10²⁰ = 82.47x10⁸ kg

substituting in equation E =[(dm/mdt)+k]m

we get,

E = (0.0487+0.01) x 82.47x10⁸

   = 0.0587 x 82.47x10⁸

   = 4.84x10⁸ kg yr^-1