Consider the reaction: H 2 ( g )+I 2 ( g )2HI( g ) A reaction mixture at equilib
ID: 988008 • Letter: C
Question
Consider the reaction:
H2(g)+I2(g)2HI(g)
A reaction mixture at equilibrium at 175 K contains PH2=0.958atm, PI2=0.877atm, and PHI=0.020atm. A second reaction mixture, also at 175 K, contains PH2=PI2=0.629 atm , and PHI= 0.101 atm .
Is the second reaction at equillibrium? I found that the kp=4.76X10-4 and Qp = .0257 So no, not at equillibrium.
If not, what is the partial pressure of HI when the reaction reaches equilibrium at 175 K? I need help figuring out the ICE chart and how to set up the equation to solve for the partial pressure of HI for the second reaction.
Explanation / Answer
We see that Qp > Kp for the reaction, hence the reaction will move in Backward direction
H2 (g) + I2 (g) ---> 2 HI (g)
0.629....0.629.........0.101
+X.........+X.............-2X
0.629+X..0.629+X...0.101-2X
Kp = 4.76 x 10^-4 = (0.101-2X)^2 / (0.629+X)^2
Taking square roots on both sides
=> (0.101-2X) / (0.629+X) = 0.0218
=> 0.101 - 2X = 0.0137 + 0.0218 X
=> X = 0.0432 atm
partial pressure of HI when the reaction reaches equilibrium at 175 K = 0.101 - 2X = 0.0147 atm