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Topic: ppm problems  (Read 8339 times)

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buffydvamp

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ppm problems
« on: September 13, 2005, 12:16:38 AM »
Hello everyone!  I need help in solving the following problems:

1) Convert 400 ppm of SO2 gas to percent by volume.  MW SO2 = 64.

2) 5 ml of CO2 is added to a plastic bag into which 47 L of pure air are metered.  What is the concentration of CO2 in the bag in ppm?

For # 1, I used the formula C(ppm)= m(mg/m3)/M x 24.45, where M is the molecular weight and m is the concentration of gas.  I am coming up with 1047 mg/m3, but I am not sure how to convert it in percent by volume.  (Ramachandran, Occupational Exposure Assessment for Airborne Contaminants).

For # 2, if I divide 0.005 L/47 L, I come up with 0.00010638, but I am not sure how to convert it to ppm.  Shall I multiply it by 1,000,000?

I hope to receive responses from you.  Thanks a lot!

Regards,
Buffy
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Offline Borek

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Re:ppm problems
« Reply #1 on: September 14, 2005, 06:09:51 AM »
Quote from: buffydvamp on September 13, 2005, 12:16:38 AM
Convert 400 ppm of SO2 gas to percent by volume.  MW SO2 = 64.

I used the formula C(ppm)= m(mg/m3)/M x 24.45, where M is the molecular weight and m is the concentration of gas.  I am coming up with 1047 mg/m3, but I am not sure how to convert it in percent by volume.

You know that 1 kg of gas contains 400 mg of SO2 - there is no problem with calculating SO2 volume (pV=nRT), but not knowing molar mass of the other gas you can't properly solve the question. 1kg (999.6g to be precise) of hydrogen is 11200 L, the same mass of Xe has a volume of 171 L.

Quote
5 ml of CO2 is added to a plastic bag into which 47 L of pure air are metered.  What is the concentration of CO2 in the bag in ppm?

If I divide 0.005 L/47 L, I come up with 0.00010638, but I am not sure how to convert it to ppm.  Shall I multiply it by 1,000,000?

To obtain vol/vol ppm - yes. To obtain mass/mass you have to calculate masses of both gases.
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themark

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Re:ppm problems
« Reply #2 on: September 14, 2005, 10:57:46 AM »
hello buffy,

question 1:  

assuming that the formula used applies to this problem, then 1m^3 of gas ( SO2 + whateverelse)contains 1041 mg of SO2.  You can the used the density of SO2 to calculate volume of SO2 and thus % by volume.  

hopes this helps

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