Help! Destroyer GenChem #146

[dentalgirlyay]

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I do not understand this problem at all in the destroyer book for gen Chem problem 146

N2 +3H2 -> 2NH3
If 8 moles of N2 and 8 moles of H2 are placed in a 2 liter flask, and allowed to come to equilibrium. At equilibrium 2 moles of NH3 are formed. calculate the Keq

why is it that N2 and 3H2 is 4-X and 4-3x while 2NH3 is 1M? and where did they get 2X=1 X=0.5 from???? Help please!

 

[MattEvers]

The coefficient of each term is used as the coefficient for x. Therefore, the nitrogen loses 1x (or just x) and the hydrogen loses 3x. The product side (ammonia) gains 2x. This may seem counterintuitive that 4x is lost on one side and only 2x is gained on the other, but you have to consider both products are needed to make the reactants, so naturally there is less product than reactant (as far as x goes).

As to where 2x=1 comes from: there are 2 moles of product in a 2 liter container. That means that 1 M of ammonia was made, so 1 M has to be equal to the amount made, in this case, 2X.

Since you started with 4 moles of nitrogen and hydrogen, and lost x and 3x respectively, you can then figure out the Keq by solving for x and subtracting what was lost from both nitrogen and hydrogen. Plug these values into the Keq equation and you have Keq.

That may have been a confusing answer. Let me know if you have any other questions.

 

[giant]

"As to where 2x=1 comes from: there are 2 moles of product in a 2 liter container. That means that 1 M of ammonia was made, so 1 M has to be equal to the amount made, in this case, 2X."

Can you please explain this part again? 😕 Thanks! I have a lot of trouble solving Keq problems using a SCE chart. I used to know this stuff very well, but I guess it's been too long! 🙁