A gas, collected by water displacement, occupies #781# #cm^3# at #14°C# and #99.1# #kPa#. What volume will the dry gas occupy at STP?

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Answer 1 · 2018-06-22T19:09:05

The question is INCOMPLETE...we need #P_"saturated vapour pressure"# at #14# #""^@C#...we also need to specify #"STP"#...

#P_"SVP"=12.0*mm*Hg# at #14# #""^@C#

Now the quoted pressure is …….

#(99.1*kPa)/(101.3*kPa*atm^-1)xx760*mm*Hg*atm^-1=743.5*mm*Hg#

And #P_"Total"=P_"SVP"+P_"gas"#

#P_"gas"=P_"Total"-P_"SVP"=(743.5-12.0)*mm*Hg=731.5*mm*Hg#

And #"STP"# specifies a pressure of #0.987*atm-=750.2*mm*Hg#, and #T-=273.15*K#

That out of the way...#(P_1V_1)/T_1-=(P_2V_2)/T_2#

We solve for #V_2=(P_1V_1)/T_1xxT_2/P_2#

#(743.5*mm*Hgxx781*cm^3)/(287*K)xx(273.15*K)/(750.2*mm*Hg)#

#=736.6*cm^3#...