After 0.600 L of Ar at 1.29 atm and 223 degrees Celsius is mixed with 0.200 L of O2 at 535 torr and 106 degrees Celsius in a 400.-mL flask at 23 degrees Celsius, what is the pressure in the flask?

1 Answer
Jul 7, 2017

Concept of partial pressure is to be applied here.

Let the partial pressure of ArAr in the final mixture be p_"Ar"pAr

Initially before mixing ArAr had

Pressure P_"Ar"=1.29PAr=1.29 atm

TemperatureT_"Ar"=223+273=500TAr=223+273=500 K

Volume V_"Ar"=0.600VAr=0.600 L

In the mixture it acquires

Pressure p_"Ar"=?pAr=? atm

Temperature T_"mAr"=23+227=250TmAr=23+227=250 K

Volume V_"mAr"=0.400VmAr=0.400 L

So by combined Boyle's and Charles's equation for ideal gas we can write

(p_"Ar"xxV_ "mAr")/T_"mAr"=(P_"Ar"xxV_"Ar")/T_"Ar"pAr×VmArTmAr=PAr×VArTAr

=>p_"Ar"=(P_"Ar"xxV_"Ar")/T_"Ar"xxT_ "mAr"/V_"mAr"pAr=PAr×VArTAr×TmArVmAr

=>p_"Ar"=(1.29xx0.600)/500xx250/0.400=0.9675pAr=1.29×0.600500×2500.400=0.9675 atm

Again let the partial pressure of O_2O2 in the final mixture be p_(O_2)pO2

Initially before mixing O_2O2 had

Pressure P_(O_2)=535PO2=535 torr ~~0.5350.535 atm

TemperatureT_(O_2)=106+273=379TO2=106+273=379 K

Volume V_(O_2)=0.200VO2=0.200 L

In the mixture it acquires

Pressure p_(O_2)=?pO2=? atm

Temperature T_(mO_2)=23+227=250TmO2=23+227=250 K

Volume V_(mO_2)=0.400VmO2=0.400 L

So by combined Boyle's and Charles's equation for ideal gas we can write

(p_(O_2)xxV_ (mO_2))/T_(mO_2)=(P_(O_2)xxV_(O_2))/T_(O_2)pO2×VmO2TmO2=PO2×VO2TO2

=>p_(O_2)=(P_(O_2)xxV_(O_2))/T_(O_2)xxT_ (mO_2)/V_(mO_2)pO2=PO2×VO2TO2×TmO2VmO2

=>p_(O_2)=(0.535xx0.200)/379xx250/0.400=0.1765pO2=0.535×0.200379×2500.400=0.1765 atm

So total pressure in the flask

P=p_"Ar"+p_(O_2)=0.9675+0.1765=1.144P=pAr+pO2=0.9675+0.1765=1.144 atm