QUESTION: Follow the logic of Worked Problem 8.1 about running out of O2, and calcultate the percetnage increase in teh atmosperic CO2 if all the fossil C ended up in the air.
***Worked Problem 8.1---Q. Some people are concerned that we will use up earth's O2 supply if we burn all the fossil fuels. Are they right to worry? ANSWER: 1)to decide this question, first calculate how many moels of O2 would be used up, given that the energy abailable in recoverable fossil fuels is estimated to be 3.7x10^19kJ and that ~407 kJ are released per mole of O2, on average, when fossil fuel is burned. (this value differs from 450kJ absorbed in reaction, because fossil fules differ in composition from carbohydrates. Dividing 3.7x10^19 kj by 405 kJ mol-1 of O2 gives 9.1x10^16 mol of O2.
(2) Next, calculate what fration of the atomosphere O2 this represents, using the following facts: the atmosphere weighs 1000 g for each square centimeter (cm^2) of earths surface, and is 21% O2 by weight the radius of earth (r) is 6.4x10^6 meters (m). Since each square centimeter (cm^2) of the earth's surface accounts for 1000g of air, or 210 g of O2 we need to know the surface area. This value can obtained from the radius using the formula for the area of a sphere, a=(r^2) x 4(pie)/3 r is given as 6.4x10^6 m, which we need to convert to centimeteres by mulitply by 100 cm m^-1. then we multiply the area (in cm^2) by the weight of O2 per cm^2, and finally divide by the molecular weight of O2 (32 g mol^-1) to find the number of moles: mol O2 =(6.4 x 10^6 x 100 cm m^-1)^2 x 4pie/3 [210 g/(32 g mole^-1)] = 113x10^17 mol
This value is 125 times greater than the answer in part (1)*****
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