[ashee805]

calculate the equal constant for the following reaction:

 2A -----> B + 3C  all gases

given that a 1.0 vessel was initially filled with 5.0 atm of pure A and the partial pressure of gas A was fpund to be 3.5 atm at equalib.

i did this:

  2A ----->  B + 3C
I 5.0          0    0

C -2x         +x  +3x

E 5-2X         X     3X


A=  5-2(3.5) = -2  

I SET IT UP AND SOLVED FOR Kc  but didnt get the answer which, btw, is 0.70 atm.  neeeed *delete me*  thanks.

[Donaldson Tan]

in cases of gas, it's called Kp , not Kc, because you use partial pressure instead of concentration to calculate the equilibrium constant.

your ICE table is right, but not your calculation. let x be the partial pressure of B.

partial pressure of A at eqbm = 5 - 2x = 3.5atm

2x = 5 - 3.5 = 1.5atm
x = 0.75atm

partial pressure of B = x = 0.75atm

partial pressure of C = 3x = 2.25atm

Kp = (C³*B)/A² =  (2.25³*0.75)/3.5² = 0.6973 ~ 0.70atm