Question

The global warming potential for CH₄ is 25. This implies that 1.0 g of methane traps the same amount of thermal energy in the atmosphere as 25.0 g of Co₂ (g) do.

a) estimate # of molecules oc CO₂ that would be needed to trap as much thermal energy as 1 molecule of CH4.

b) estimate number of molecules of CO₂ that would be needed to trap as much thermal energy as 1 molecule of N₂O

c) estimate number of molecules of CO₂ that would be needed to trap as much thermal energy as 1 molecule of CCI₂F₂

₃₎ What would be the advantages and disadvantages of expressing GWP as thermal energy trapped per molecule rather than per gram of substance?

Answer 1

WKT 1 mole = 6.023 x 10²³   number of molecules (Avogadro's Number)

1 gm of CH₄ = 25 g of CO₂

Molecular weight of CH₄ = 16 ; Molecular weight of CO₂ = 44

WKT mole=weight / Molecular weight

In case of 1 gm of CH₄; mole= 1/16=0.0625 mole or 0.3764 x 10²³ molecules

In case of 25 g of CO2; mole=25/44=0.5681 mole or 3.4216 x 10²³ molecules

Thus,

a) Nearly 9 molecules of molecules CO₂ that would be needed to trap as much thermal energy as 1 molecule of CH4.

b) The global warming potential for N₂Ois 298.Its molecular weight is 44.

1 gm of N₂O = 298 g of CO₂

0.02272 mole of N₂O = 6.7727 mole of CO₂

0.1368 x 10²³ molecules of N₂O =40.7919 x 10²³ molecules of CO₂

thus, 298 number of molecules of CO₂ that would be needed to trap as much thermal energy as 1 molecule of N₂O

c) 10,900 number of molecules of CO₂ that would be needed to trap as much thermal energy as 1 molecule of CCI₂F₂