A 1.50 liter flask at a temperature of 25°C contains a mixture of .158 moles of methane, .09 moles of ethane, and .044 moles of butane. What is the total pressure of the mixture inside the flask?

1 Answer
anor277
Oct 8, 2016

#P=(nRT)/V~=5*atm#

Explanation:

Dalton's law of partial pressures holds that in a gaseous mixture, (i) the partial pressure of any component gas is the same as the pressure it would exert if it ALONE occupied the container; and (ii) that the total pressure is the sum of the individual partial pressures.

Thus #P_"total"# #=# #P_"methane"+P_"ethane"+P_"butane"#, and if we (reasonably) assume ideality, then:

#P_"total"# #=# #(n_"total"xx0.0821*L*atm*K^-1*mol^-1xx298*K)/(1.50*L)#

where #(n_"total"=n_"methane"+n_"ethane"+n_"butane")# #=#

#(0.158+0.09+0.044)*mol# #=# #0.292*mol#

And so, #P_"total"# #~=# #5*atm#. You will be able to make a better estimate.

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