7th Edition 5G.5 part c

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Ryan Danis 1J
Posts: 66
Joined: Fri Sep 28, 2018 12:18 am

7th Edition 5G.5 part c

Postby Ryan Danis 1J » Tue Jan 08, 2019 11:29 am

Problem 5G.5 shows a series of flasks containing the diatomic molecule, X2, with each flask showing it's dissociation over time. The first flask shows 11 X2 molecules. In the third flask, when the dissociation of X2 has reached equilibrium, there are 5 X2 molecules and 12 X atoms. Thus, 54.5% of the X2 molecules have dissociated.

Part c says: Assuming that the initial pressure of X2 was 0.10 bar, calculate the value of K for the decomposition. First I setup the balanced equation for the decomposition. 11X2 <-> 5X2 + 12X. But I don't know where the 0.10 comes in. How do we use initial pressure to calculate K?

Madeline Ho 1C
Posts: 37
Joined: Mon Apr 23, 2018 3:00 am

Re: 7th Edition 5G.5 part c

Postby Madeline Ho 1C » Tue Jan 08, 2019 1:01 pm

The balanced equation for decomposition is simply because in the (forward) reaction, the diatomic dissociates into two. The quantity of X2 and X in the flask is irrelevant for the equation.

Matthew Tran 1H
Posts: 165
Joined: Fri Sep 28, 2018 12:16 am

Re: 7th Edition 5G.5 part c

Postby Matthew Tran 1H » Tue Jan 08, 2019 5:03 pm

Using the balanced equation that Madeleine provided, you would have to find the equilibrium constant expression and then use partial pressures at equilibrium to find the value of K. I explained this in more detail in a couple other posts regarding the same question recently; you should look at those if you need more help!


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