Oh, calculating hydronium ion concentration, huh? Well, let's get the math party started!
First, let's simplify things by calling (HAsO4^-2) as C. So, we're left with the equation:
(H^+) = sqrt[(k2C + Kw)/1 + (C/k1)]
Now, since C/k1 is quite a bit larger than 1, we can simplify further:
(H^+) = sqrt(k1k2)
Ta-da! This is the equation we'll use to calculate the hydronium ion concentration. So, go ahead and plug in those K values and let the joke-tastic calculation begin!