Chapter 14
Q. 14-5
Preparing a Metal Ion Buffer
What concentration of EDTA should be added to 0.010 M CaY^{2−} at pH 6.00 to give [Ca^{2+}] = 1.0 × 10^{−6} M?
Step-by-Step
Verified Solution
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)