Edta is often used to preserve blood samples because it complexes with ca2 , making ca2 unavailable for its usual role in clotting. the typical concentration of ca2 in blood is 1.1  10–6 m. the ph of blood is 7.2 and the relevant alpha fractions for free edta at this ph are 2.0  10–10, 3.0  10–6, 0.12, 0.88, and 8.1  10–4 for h4y, h3y–, h2y2–, hy3–, and y4–, respectively. (the amount of edta in the forms of h5y and h6y2 at this ph are very small and can be neglected.) the formation constant for cay2– is 4.47  1010. na2h2y is added to a 2.0 ml blood sample so that the initial edta concentration (before complexation) equals 5.0  10–3 m and the initial calcium concentration is 1.1  10–6 m. find [ca2 ], [y4–], [cay2–], [edta], and [hy3–] in the sample of blood. remember that [edta] refers to the total concentration of free (uncomplexed) edta.