A tragedy occurred at Lake Nyos in Cameroon (Africa) during the summer of 1986 .

Question

A tragedy occurred at Lake Nyos in Cameroon (Africa) during the summer of 1986 . During the process of unraveling this mystery scientists had to rely on basic concepts of gas behavior which they most likely learned in a general chemistry class. Moreover, the PV=nRT equation was an especially important tool used by the scientists to help determine what happened in this tragedy.

1. Determine the weighted average for the molar mass of dry air assuming the approximate compositions below. N2 , 78%, O2, 21%, Ar, 1%

2. Calculate the density of dry air using the result from above and the d = PM/RT equation. Assume the overnight conditions during this tragedy were as follows: pressure , 1 atm and the temp., 18 degree C.

3. Calculate the density of carbon dioxide gas using the d = PM/RT equation. Assume the same conditions as specified in #2 above.

Explanation / Answer

I'll help you with question 1 and 2. The number 3 is similar as the question 2, so, try to answer it yourself.

1. The average molar mass, let's assume we have 1 g of the mixture of air so:

N2 = 0.78 g; O2 = 0.21 g; Ar = 0.01 g

The individual molar mass of them are:

N2 = 14*2 = 28 g/mol; O2 = 16 * 2 = 32 g/mol; Ar = 39.95 g/mol

Avrg MM = (0.78 * 28) + (0.21 * 32) + (0.01 * 39.95) = 28.9595 g/mol

2. d = P * MM / RT

d = 1 atm * 28.9595 g/mol / 0.082 L atm * (18+273)

d = 1.2136 g/L

For question 3, just use the molecular mass of CO2, and calculate density. Hope this helps.

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