The equilibrium constant for the following gas phase reaction is 4.0 at a certain temperature. A reaction is carried out at this temperature starting with 2.0 mol/L of CO and 2.0 mol/L of H2O. What will be the equilibrium concentration of H2? CO + H2O CO2 + H2 a). 2.0 M b). 0.75 M c). 1.3 M d). 0.67 M e). 1.5 M The answer is C. I.3M apparently. But I am not getting the answer. Can anyone how me how to get this? Please and thank you!

Question

The equilibrium constant for the following gas phase reaction is 4.0 at a certain temperature. A reaction is carried 
out at this temperature starting with 2.0 mol/L of CO and 2.0 mol/L of H2O.
 
What will be the equilibrium 
concentration of H2?
CO + H2O<----> CO2 + H2
a). 2.0 M b). 0.75 M c). 1.3 M d). 0.67 M e). 1.5 M
The answer is C. I.3M apparently. But I am not getting the answer. Can anyone how me how to get this? Please and thank you!

aaronq · Answer

did you write an ice table?

aaronq · Answer

CO + H2O<----> CO2 + H2
i   2       2                 0          0
c   -x    -x                 +x      +x
e  2-x    2-x              x         x

K=[CO2][H2]/[CO]

aaronq · Answer

i don't think you need to to include water vapour, but do so if it doesn't work the way i wrote it.

anonymous · Answer

Oh! I forgot about the ICE method! I just worked out the problem and got the correct answer. I see where I went wrong now! Thanks!!
I set it up like this:
4=$$\frac{ x ^{2} }{ (2-x)^{2} }$$
and I solved and got 1.3M just like the answer was supposed to be!

aaronq · Answer

awesome, dude ! np