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### Finding Ka

Posted: Sun Feb 12, 2017 10:14 pm
I was doing a practice midterm (2014) and I got stuck on #8 because it asked for Ka. Based on the answer, you're just supposed to take the square root of K. Is there also a relationship between K and Kb? Are there other relationships we are supposed to know?

### Re: Finding Ka

Posted: Sun Feb 12, 2017 10:46 pm
Kb would apply to a basic reaction, so I assume that you would solve it the same way as you would for an acidic reaction.

### Re: Finding Ka

Posted: Wed Feb 15, 2017 12:20 am
Ka is the k value of the decomposition of a weak acid (i.e., it is the dissociation constant) it is calculated the same way as K for the rxn. A square root is taken in this equation, because the redox reaction has everything doubled, and the Ka is based on the simplest version of the rxn. We had to double all of the parts to get the number of electrons right, which resulted in them being squared when calclating K, so we had to take a squre root to undo this and get Ka.