Question

What volume of air is needed to burn an entire 60-L (approximately 16-gal) tank of gasoline? Assume that the gasoline is pure octane, C8H18. Hint: air is 20% oxygen by volume, 1 mol of a gas occupies about 25 L at room temperature, and the density of octane is 0.70 g/cm3.

Answer 1

I think you can look at this problem like this.

Each year it is 2,16 * 10^13 kg more CO2 put into the atmosphere, and this is
2,16*10^13/4,5*10^15 = 0,005 increase.

So if you use a simple interest formula you should get the right answer. (same growth each year)

4,5 * 1,005^x = 9 (10^15 cancels out)
1,005^x = 2
x*log(1,005) = log(2)
x = log(2)/log(1,005)
x = 139

So it would take 139 years for the CO2 amount to double in the atmosphere, with the current use of fossil fuel.