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4. Assume the Earth is a sphere with radius of 6370 km. (a) If the atmospheric p

ID: 883899 • Letter: 4

Question

4. Assume the Earth is a sphere with radius of 6370 km. (a) If the atmospheric pressure is 1013.25 hPa and the average molecular weight of air is 28.96 kg/kmole, determine the number of molecules of air in the atmosphere. Hint: According to Avogadro, a kmole of any gas contains 6.022 X 10^26 molecules of that gas. (b) It has been estimated that about 3.4 x 10^13 kg of fossil fuels will be consumed annually by the year 2020. If one-third the resulting carbon dioxide remained in the atmosphere, what would be the annual rate of increase in atmospheric carbon dioxide (in parts per million by volume) around the year 2020? Assume that the fuels are 75% carbon by mass and that each carbon atom is used to form a carbon dioxide molecule. Hint: Carbon has a molecular weight of 12 kg/kmole.

Explanation / Answer

To calculte no of molecules in air we have to calculate no of mole of air(weight of air to be find out from pressure and radius of sphere

Pressure = weight / area

A = 4r2

   = 4 *3.14* 63702 = 509645864 km2

weight = 10332.27*106 * 509645864 kg ( since 1013.25hpa = 1.0332.27 kg/cm2)

now Number of kmoles = weight / molecular weight

                                   = 5.269*1014 / 28.96

                                   = 1.82 *1013

Number of molecules in air = Moles of air * Avagadro number(one mole = avagadro number of molecules)

                                           =1.096 * 1040

Sorry, b) i couldn't solve

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