Question

1.) If everyone in the world planted a tree today, how long would it take for these trees to decrease the
concentration of CO2 by 1 ppm? Assume that 9 kg of O2 is produced per tree each year regardless of age,
and the CO2 and H2O combine through photosynthesis to form biomass (C6H12O6) and O2. Also assume
that the CO2 that can be assimilated is only in troposphere, which extends 17 km above the surface of the
Earth, and the average temperature and pressure of the troposphere are 273 K and 0.6 atm, respectively

Answer 1

6 CO2 + 6 H2O -----------------------> C6H12O6 + 6 O2

264 g 192 g

264 g ----------------------------> 192 g O2

x g ---------------------------------> 9000 g O2

x = 264 x 9000 / 192

x = 12375 g CO2 consumed in a year for given O2

CO2 concentraton to reduce = 1ppm = 1mg / L = 10^-3 g /L = 10^-3 / 44 M = 2.27 x 10^-5 M

PV = n R T

n / V = P / RT

n / V = 0.6 / 0.0821 x 273 = 0.0268 M

molarity reduced =   2.27 x 10^-5 / 0.0268 = 8.48 x 10^-4 M

8.48 x 10^-4 moles = 8.48 x 10^-4 x 44 g = 0.0373 g

12375 g CO2 consumed in a year for given O2

0.0373 ----------------------> ??

331650 years it will take