Photosysthesis si a bio process by which plants make energy rich molecules from low energy molecules with the help of energy from sunlight . The photosysthesis of glucose can be represented as:
`6CO_(2(g))+ 6H_(2)O_(g) + hv rarr C_(5)H_(12)O_(6(s)) + 6O_(2)(g)..........(i)`
The energy of one mole of a photon of wave lenght is known as one Einstein.
On an average , solar radiation `7 xx 10^(14)` kg of glucose annually on earth . Calculate the annual decrease in the `CO_(2)` level in the troposphere in ppm , due to photosynthesis. (1 ppm=1 g of `CO_(2)` per `10^(3)` kg of air in troposhere). Assume that the total mass of air envolope surrounding the earth is `5.0 xx 10^(15)` kg and 80% of its is present in the tropsphere.

Answer

`n_("glucose") = (7 xx 10^(17)) = 3.89 xx 10^(15)`
`therefore n_(CO_(2)) = 3.89 xx 10^(15) xx 6 = 2.34 xx 10^(16)`
`therefore W_(CO_(2)) = 2.34 xx10^(16) xx 44=1.02 xx 10^(18)` gm
Total mass of air in troposphere `=5xx10^(15) xx 0.8 = 4 xx 10^(15)`
`because 4 xx 10^(15)` kg of air `=1.02 xx 10^(18)`
`therefore 10^(3)` kg of air `= (1.02 xx 10^(18) xx 10(3))/(4 xx 10^(15)) = 2.56 xx 10^(5)` ppm.