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.

A. . Determine the weighted average for the molar mass of dry air assuming the approximate compositions below.

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

B. 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 C.

Explanation / Answer

A) Given that N2 , 78%, O2, 21%, Ar, 1%

We know that molar mass of N2 = 28 g/mol

molar mass of O2 = 32 g/mol

molar mass of Ar = 40 g/mol

Hence,

weighted average for the molar mass of dry air = ( 0.78 x 28 ) + (0.21 x 32) + ( 0.01 x 40) g/mol

= 28.96 g/mol

B) density d = PM/RT , R = 0.0821 L.atm/mol/K

Given that T = 18oC = 18 + 273 K = 291 K

P = 1 atm

M = 28.96 g/mol

Hence,

d = PM/RT

= [1 atm x 28.96 g/mol ]/ [ 0.0821 L.atm/mol/K x 291 K ]

= 1.212 g/L

d = 1.212 g/L

Therefore,

density of dry air = 1.212 g/L

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.