Quiz 3 Prep Fall 2014 #10

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Joined: Wed Sep 21, 2016 3:00 pm

Quiz 3 Prep Fall 2014 #10

Postby Michelle_Li_1H » Tue Nov 15, 2016 5:33 pm

For the following reaction, if initially 0.100 mol of H2O (g) is placed in a 4.0 L vessel, what is the equilibrium partial pressures of each reactant and of each product?
H2O (g) + C(s) <-> H2 (g) + CO (g)
Kp = 3.72 at 1000 K

For the question stated above, I found the molarity for H2O, 0.025 M, and set up the equation to solve using the quadratic equation (x2 + 3.72X - 0.093 = 0). I got .0248 mol/L for H2 and CO, and 1.657x104 mol/L for H2O.

I then used the P=MRT to solve for the partial pressure (2.04 atm and 0.0136 atm), however I got a different answer than the solutions (1.47 atm and 0.58 atm).

Could someone look over my work and tell me what I did wrong? Thanks!

Amy Ko 3C
Posts: 24
Joined: Sat Jul 09, 2016 3:00 am

Re: Quiz 3 Prep Fall 2014 #10

Postby Amy Ko 3C » Tue Nov 15, 2016 8:24 pm

Solve for pressure from PV=nRT first since you are given Kp (not Kc)!
When you use the ICE BOX, you should use it on partial pressure of the reactants and products.

Derek Lee 2K
Posts: 30
Joined: Sat Jul 09, 2016 3:00 am

Re: Quiz 3 Prep Fall 2014 #10

Postby Derek Lee 2K » Wed Nov 16, 2016 12:31 am

I did that but I still end up with a value for x that is too small. What numbers did you have after doing PV=nRT?

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