A rigid tank is divided into two compartments by a partition. One compartment contains 2 kmol of N₂ at 500 kPa pressure and the other compartment contains 8 kmol of CO₂ at 200 kPa. Now the partition is removed, and the two gases form a homogeneous mixture at 300 kPa. The partial pressure of N₂ in the mixture is A)41 kPa B)60 kPa C)150 kPa D)115 kPa E)225 kPa

Question

Quizplus · Accepted Answer

Solved by EES Software. Solutions can be verified by copying-and-pasting the following lines on a blank EES screen. 
P1 = 500 "kPa"
P2 = 200 "kPa"
P_mix=300 "kPa"
N1=2 "kmol"
N2=8 "kmol"
MM1=28 "kg/kmol"
MM2=44 "kg/kmol"
N_mix=N1+N2
y1=N1/N_mix
y2=N2/N_mix
P_N2=y1*P_mix
"Some Wrong Solutions with Common Mistakes:"
W1_P1= P_mix/2 "Assuming equal partial pressures"
W2_P1= mf1*P_mix; mf1=N1*MM1/(N1*MM1+N2*MM2) "Using mass fractions"
W3_P1 = P_mix*N1*P1/(N1*P1+N2*P2) "Using some kind of weighed averaging"

A Rigid Tank Is Divided into Two Compartments by a Partition