Partial Pressure vs Molarity

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Natalie Yakobian
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Joined: Fri Sep 25, 2015 3:00 am

Partial Pressure vs Molarity

Postby Natalie Yakobian » Wed Nov 11, 2015 2:11 am

Hi,
When were dealing with a Equilibrium Constant problem where all products and reactants are gas do we have to first convert to partial pressure and then solve it, or are we allowed to convert to molarity to solve it?

For example in the book Example 11.8 we are given grams of gas and a volume. The book solves it by going from solving for mols to solving for partial pressure and then solving for unknown concentrations in partial pressure. The given K isn't specfied as Kp or Kc.

What I would have done is go straight to converting into M and solved for the unkown Molarities using K. Could I have done this and get the right answer?

Thanks so much.

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Re: Partial Pressure vs Molarity

Postby Chem_Mod » Wed Nov 11, 2015 9:37 am

In the text book, using partial pressures to calculate the equilibrium constant will give "K" and using molarities to calculate the equilibrium constant will give "Kc"(subscript c). You can choose to do either way, but you need the conversion between K and Kc, which can be found on page 438 in your text book.


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