1. Ideal gas law and molar mixing ratios a. CO2 molar mixing ratios are 400 ppmv
ID: 700890 • Letter: 1
Question
1. Ideal gas law and molar mixing ratios
a. CO2 molar mixing ratios are 400 ppmv. What is this as a percent abundance?
b. CFC-11 molar mixing ratios are 250 pptv. What is this as a percent abundance?
c. Calculate the ozone concentration in µg/m3 for a polluted day in Mexico City (200 ppbv ozone, temperature = 30 °C, pressure = 0.77 atmospheres pressure).
d. Helium gas contains trace amounts of methane (helium is obtained from some oil and gas wells and is a non-renewable resource). Consider a helium balloon pressurized to 5 psi. If the methane molar mixing ratio is 800 ppmv, what is the pressure of methane in the balloon?
Explanation / Answer
Ans 3
Pressure P =0.77 atm
Temperature T= 30 + 273 = 303 K
Gas constant R = 0.0821 L-atm/mol-K
From the ideal gas equation
Volume of 1 L gas in a mol
V = RT/P
= 0.0821 x 303/0.77
= 32.31 L/mol
Molecular weight of ozone = 48 g/mol
Concentration in ppm = 200 ppbv x 0.001 ppmv/ppbv
= 0.2 ppmv x (1 ppm)/(29/48)ppmv
= 0.331 ppm
Concentration in µg/m3
= concentration in ppm x molecular weight / V
= (0.331 x 48 ) /(32.31)
= 0.4917 mg/m3 x (1000µg/mg)
= 491.7 µg/m3
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