Problem 11.81

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Andy Liao 1B
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Joined: Thu Jul 13, 2017 3:00 am

Problem 11.81

Postby Andy Liao 1B » Sun Dec 03, 2017 4:55 pm

Problem:
11.81 A gaseous mixture consisting of 2.23 mmol N2 and 6.69 mmol H2 in a 500.-mL container was heated to 600. K and allowed to reach equilibrium. Will more ammonia be formed if that equilibrium mixture is then heated to 700. K? For N2(g) + 3 H2(g) ⇋ 2 NH3(g), K = 1.7 x 10^3 at 600. K and 7.8 x 10^5 at 700. K.

I was wondering why the reaction favors the formation of reactants. I thought that if additional heat is added while forming product, the heating will favor the formation of product. Can someone please clarify?

MichelleKaku1H
Posts: 21
Joined: Fri Sep 29, 2017 7:04 am

Re: Problem 11.81

Postby MichelleKaku1H » Sun Dec 03, 2017 5:04 pm

Since the equilibrium constant at 600.K (1.7 x 10^-3) is greater than the equilibrium constant at 700.K (7.8 x 10^-5), less ammonia will be formed with the higher temperature. Therefore raising the temperature will favor the formation of reactants. Hopefully this clarifies it!

Emma Miltenberger 2I
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Joined: Thu Jul 27, 2017 3:00 am

Re: Problem 11.81

Postby Emma Miltenberger 2I » Mon Dec 04, 2017 12:06 pm

The reaction will favor the direction that makes the reaction endothermic. In this case, the formation of reactants is favored because it makes the reaction endothermic as opposed to exothermic.

soniatripathy
Posts: 50
Joined: Thu Jul 13, 2017 3:00 am

Re: Problem 11.81

Postby soniatripathy » Tue Dec 05, 2017 3:15 am

One way to easily see whether products or reactants will be favored is to use the following rules:
K < 1 favors reactants
K = 1 pretty much the same favorability for reactants and products
K > 1 favors products
(an easy way to remember this is that the inequality sign favors the side of the reaction that it is pointing to)

We can now look at the two K values at 600K and 700K. Since K for 600K is closer to one and larger there will be more product formed than at 700K.


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