How many moles of gas exist for a volume of #0.125*L# collected over water at #298*K# at a pressure of #747*mm*Hg#?

1 Answer
May 2, 2016

Answer:

You need the saturated vapour pressure. This shoud have been quoted with the question.

Explanation:

Gas collected over water is saturated with water vapour. At #298# #K#, the vapour pressure of water is #23.8*mm*Hg#.

So #P_"Gas collected"# #=# #P_("butane") + P_("water vapour")#

#P_("butane")# #=# #(747-23.8)*mm*Hg# #=# #723.2*mm*Hg#.

#n# #=# #(PV)/(RT)# #=# #(((723.2*mm*Hg)/(760*mm*Hg))*atmxx0.125*L)/(0.0821*L*atm*K^-1*mol^-1xx298*K)#

#~=# #5xx10^-3*mol#.