Question 14-5: Preparing a Metal Ion Buffer. What concentration of EDTA sho...

From Equation 14-17, we write

K_{f} = 10^{10.65} = \frac{[CaY^{2−}]}{[Ca^{2+}]α_{Y^{4−}}[EDTA]}       (14-17)

[EDTA] = \frac{[CaY^{2−}]}{K_{f}α_{Y^{4−}}[Ca^{2+}]} = \frac{0.010}{(10^{10.65})(1.8 × 10^{−5})(1.00 × 10^{−6})} = 0.012_{4} M

These are practical concentrations of CaY^{2−} and of EDTA.

Test Yourself      What concentration of EDTA should be added to 0.010 M CaY^{2−} at pH 6.00 to give [Ca^{2+}] = 1.0 × 10^{−7} M? (Answer: 0.12_{4} M)