Destroyer Problem #48 Gen. Chem

[jdpaul14]

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Hey guys,

I was having a little trouble with the concept on Problem 48 of the DAT destroyer GC section.

Q: Consider the following: 2A(g) + B(g) ----> 2C(g)

0.50 atm of A and 0.20 atm of B are placed in a flask at 300K. At equilibrium the total pressure is found to be 0.60 atm. Calculate the Kp for the reaction.

A: The destroyer solution was a little vague but the answer is 4.4....can anyone explain how in the world they got this answer? Also, what type of problem is this?

Thanks in advance guys!

 

[BTtheman777]

Set up a reaction table:
2A + B --> 2C
i) .5 .2 0
c) -2x -x +2x
e)(.5-2x) (.2-x) (2x)

At equillibrium, individual partial pressures must add up to .6 as stated by the problem. Add up all the equillibrium mixtures and set them equal to .6 :
(.5-2x) +(.2-x)+(2x) = .6
x =.1

Now that you have x, plug it into the unknown equillibrium mixtures and find out the value of individual partial pressures at equillibrium. once you have the eq, conc, plug it into the Eq. equation: ((C^2)/(A^2)(B)). This should come out to be (.04)/(.1*.09), which equals 4.4.

Hope this helps.