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### Topic: Help on Ideal Gas Law  (Read 5542 times)

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#### yang09

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##### Help on Ideal Gas Law
« on: August 28, 2011, 04:07:28 PM »
Each square meter of an actively growing forest fixes on average each year 1 kg of carbon from the atmosphere into plant matter through photosynthesis. The atmosphere is approximately 20% O2 and 80% N2, but contains 0.046% CO2 by weight.

a.) What volume of air at 25oC and 1 atm is needed to provide this 1 kg of carbon?
b.) How much carbon is present in the entire atmosphere lying above each square meter of the earth's surface? (Hint: 1 atm is equivalent to 1.0332 X 104 kg/m2
c.) At the current rate of utilization, how long would it take to use all the CO2 in the entire atmosphere directly above a forest

#### yang09

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##### Re: Help on Ideal Gas Law
« Reply #1 on: August 28, 2011, 04:40:33 PM »
I am having trouble incorporating the 1 kg of Carbon to the percent weight of CO2 in the atmosphere. I know that the percent weight formula for CO2 is 0.046 = [mass of CO2/Total mass in atmosphere(Nitrogen + oxygen + dioxide)] X 100, but that does not relate to the weight of Carbon at all.
I know that I will have to use the ideal gas law and the unknown will be "n". I'm assuming that "n" is the moles of Carbon and that to get that, I have to somehow use the weight percent of Carbon Dioxide(0.046%) and through stoichiometry, convert it to the moles of carbon. The problem is that I do not know how to go from the weight percent to moles of carbon.

#### fledarmus

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##### Re: Help on Ideal Gas Law
« Reply #2 on: August 31, 2011, 01:03:15 PM »
I know that I will have to use the ideal gas law and the unknown will be "n". I'm assuming that "n" is the moles of Carbon and that to get that, I have to somehow use the weight percent of Carbon Dioxide(0.046%) and through stoichiometry, convert it to the moles of carbon. The problem is that I do not know how to go from the weight percent to moles of carbon.

You started out okay, then got lost. You can go directly from the mass of carbon to the moles of carbon to the moles of carbon dioxide to the weight of carbon dioxide. Then you can use the weight percent to find the moles of everything else, and the ideal gas law to find the total volume.