The question is "Calculate [HY
3-] in a solution prepared by mixing 10.0 mL of 0.01 M VOSO
4, 9.90 mL of 0.01 EDTA, and 10.0 mL of buffer with a pH of 4.00".
The answer is to first find [VO
2+], [VOY
2-], and then [Y
4-] (= [VOY
2-]/([VO
2+] x K
6)) and use that to find [HY
3-] which is through the equation ([H
+][Y
4-])/K
6I just don't understand why we are using K
6 (derived from pK
6 of H6Y
2+) and using that equation to find HY
3-. Is this what we do if we want to find any of the fractional compositions of EDTA or just for HY
3-? What made us use Y
4- instead of anything else?
Thank you!
P.S.: I posted this question yesterday but I did not format the post properly. I reposted it here now with proper formatting