How to Calculate Kp for a Sealed Vessel at Equilibrium?

[veitch]

Homework Statement

Given a sealed vessel at 2000K, initially contains I2 (g) + Cl2 (g) <- -> 2 ICl (g) with partial pressures .3 atm, .3 atm and .5 atm respectively. At equilibrium the partial pressure of ICl has increased by 52.8% (so .764 atm)... calculate Kp. But that is one part that confuses me. Does only one pressure change?

Anyway.. I just did a Kp calculation for a previous question with no change and got the proper answer (it's given)... but using an ICE table in that question allowed me to solve for x to figure out the diffferent pressures... I tried to do that here but Got:

I2 Cl2 ICl
(.3-x) (.3-x) (.5+2x)

but if I add them together and equal to the total pressure (1.1 atm) ... everything cancels out. I admit I don't have a great understanding of pressures yet... any help would be greatly appreciated.

 

[Borek]

All partial pressures change in this case.

 

[Blueshift5]

Hello,

To calculate Kp for this reaction, we first need to write the equilibrium expression:

Kp = (P_ICl)^2 / (P_I2)(P_Cl2)

Since we are given the partial pressures of each gas at equilibrium and the initial partial pressures of I2 and Cl2, we can plug these values into the equation:

Kp = (0.764 atm)^2 / (0.3 atm)(0.3 atm) = 6.37

To address your confusion about the pressure changes, it is important to note that at equilibrium, the forward and reverse reactions are still occurring, but at equal rates. This means that the partial pressures of the reactants and products may change, but the overall pressure of the system remains constant. In this case, the partial pressure of ICl has increased by 52.8%, but the total pressure remains at 1.1 atm.

In terms of using an ICE table to solve for x, it can be a useful tool for more complex equilibrium problems, but in this case, it is not necessary. The given values already allow us to calculate Kp directly.

I hope this helps clarify any confusion. Keep practicing and studying, and your understanding of equilibrium and pressure will improve. Good luck!