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Dissociation constant

If I have the following equation:

CH3COOH(aq) <-----> CH3COO-(aq) + H+(aq), and want to find the dissociation constant "ka, is it as follows:

ka = [H+][CH3COO-] / [CH3COOH]

And, the unit is mol dm-3?

Thanks.
(edited 13 years ago)
Original post by SWEngineer
If I have the following equation:

CH3COOH(aq) <-----> CH3COO-(aq) + H+(aq), and want to find the dissociation constant "ka, is it as follows:

ka = [H+][CH3COO-] / [CH3COOH]

And, the unit is mol dm-3?

Thanks.


Yes, although in reality the units are not correct as the law of mass action uses activities not concentrations. These are very close to each other in dilute solutions and for that reason most exam boards use concentrations.
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SWEngineer
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Original post by charco
Yes, although in reality the units are not correct as the law of mass action uses activities not concentrations. These are very close to each other in dilute solutions and for that reason most exam boards use concentrations.


Thanks @charco.

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