Help with Chemical Equilibrium

[Secret]

How do I find out initial amounts of a equilibrium problem if one or some of them are not given ?

 

Ex: Equilibrium is established in a 2.50-L flask at 250 degree celcius for the reaction:

 

PCl5(g) -> PCl3(g) + Cl2(g) Kc= 3.8x10^-2

 

How many moles of each molecule is present, if 0.550mol of each PCl5 and PCl3 was initially introduced into the flask?

 

.. thanks

[Borek]

Write equation for equilibrium (with the reaction quotient) first. The think what are dependences between amounts of the substances (hint: is there any dependence between amount of chlorine produced and amount of PCl₅ decomposed?). Then plug in all numbers you know and look if you can solve the equation.

 

Borek

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General Chemistry Software

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[Darkblade48]

I'm not too sure if this answers your question (I may be just interpreting it incorrectly).

 

Since you are asking for the initial amounts, you just need to read the question, as it is provided for you (... if 0.550mol of each PCl5 and PCl3 was initially introduced into the flask?)

 

Thus, you know that the initial amounts of PCl5 and PCl3 were 0.550 moles each.

 

From here, as Borek stated, you can write out your reaction equations and solve for the equilibrium amounts of the reactant and products (i.e. using an ICE table)

[Borek]

Since you are asking for the initial amounts, you just need to read the question, as it is provided for you (... if 0.550mol of each PCl5 and PCl3 was initially introduced into the flask?)

 

Missed that one

 

Borek

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General Chemistry Software

www.pH-meter.info