# Chemistry question - equilibrium constant

**URL:** <https://boards.straightdope.com/t/chemistry-question-equilibrium-constant/376430>\
**Category:** Factual Questions\
**Created:** [October 14, 2006, 3:05pm UTC](https://boards.straightdope.com/t/chemistry-question-equilibrium-constant/376430 "2006-10-14T15:05:39Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\
**Post date:** [October 14, 2006, 3:05pm UTC](https://boards.straightdope.com/t/chemistry-question-equilibrium-constant/376430/1 "2006-10-14T15:05:39Z")

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The question: In the equation for chemical equilibrium constant, [as shown here](http://en.wikipedia.org/wiki/Chemical_equilibrium), how do I read these equations?

The sample equation, I’m reading as: “m moles of A plus n moles of B yields p moles of C and q moles of D”.

So using the same values as above, the equilibrium expression, I’m reading as:  
molar concentration of C to the p power \* molar concentration of D to the q power  
divided by  
molar concentration of A to the m power \* molar concentration of B to the n power

Just as background, this isn’t homework. I am spontaneously deciding to brush up on my chem skills from 15 years ago, studying independently. I minored in chemistry but subsequently haven’t used it at all. I’m finding that while I remember many of the concepts, I see a lot of symbolic expressions that I don’t understand but the authors consider to be self-explanatory for the intended audience. So that’s why I’m asking.

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**Author:** ![Bob55](https://avatars.discourse-cdn.com/v4/letter/b/e9c0ed/32.png) [@Bob55](https://boards.straightdope.com/u/Bob55)\
**Post date:** [October 14, 2006, 3:58pm UTC](https://boards.straightdope.com/t/chemistry-question-equilibrium-constant/376430/2 "2006-10-14T15:58:00Z")

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The way you worded it sounds accurate to me. Remember that technically you need to take into account the activity of the ion for it to be truly accurate, but that is really only for people doing extremely accurate chemistry.

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**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\
**Post date:** [October 14, 2006, 9:10pm UTC](https://boards.straightdope.com/t/chemistry-question-equilibrium-constant/376430/3 "2006-10-14T21:10:38Z")

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Thanks Bob for answering my question. Thanks also for covering the unasked question about the importance of activity vs. molarity.