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

Question

A tragedy occurred at Lake N 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 expecially important tool used by the scientists to help determine what happened in this tragedy. Click on the link below and read about this incident before working the problem below. Determine the weighted average for the molar mass of dry air assuming the approximate compositions below. 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.

Explanation / Answer

‘’ Molecular weights

N2= 28 O2= 32 and Ar=40

Percentages of gases by volume

N2= 78%, O2=21% and Ar= 1%

Basis : 1 mole of dry air

Mole= mass/molecular weight

Mass= molecular weight

Mass = 0.78*28+0.21*32+0.01*40 =28.96

b)

Given P= 1atm and temperature = 18 deg.c =18+273.15= 291.15K

Given density = PM/RT, M =molecular weight = 28.96, P= 1atm, R= 0.0821 L.atm/mole.K

Density = 1*28.96/(0.0821*291.15)=1.21 g/L

3.

Dry ice undergoes sublimation and becomes vapor.

Molecular weight of CO2= 44

Desity of CO2 at STP= 44/22.4 =1.96 g/L

This is heavier than air. So try to come down. B is the correct answer.

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