Explore BrainMass
Share

Chelate with a metal ion

This content was STOLEN from BrainMass.com - View the original, and get the already-completed solution here!

In forming a chelate with a metal ion, a mixture of free EDTA (abbreviated Y^4-) and metal chelate (abbreviated MY^n-4) can buffer the free metal ion concentration at values near the dissociation constant of the metal chelate, just as a weak acid and a salt can buffer the hydrogen ion concentration at values near the acid dissociation constant.

This equilibrium is governed by the equation

Where Kf is the association constant of the metal and Y^4-, αy^4- is the fraction of EDTA in the Y^4- form, and [EDTA] is the total concentration of free (unbound) EDTA. is the "conditional formation constant."

How many grams of Na_2EDTA·2H_2O (FM 372.23) should be added to 1.51 g of Mg(NO_3)_2·2H_2O (FM 184.35) in a 500-mL volumetric flask to give a buffer with pMg^2+ = 8.00 at pH 10.00?

(log K_f for Mg-EDTA is 8.79 and αy^4- at pH 10.00 is 0.30.)

Mass Na_2EDTA*H_2O = _________________g

Hint: after I missed the answer
[Mg^2+ ] = 10^-pMg2+ = 1.0 �- 10-8 M, so essentially all of the Mg^2+ in solution is in the form MgY^2-. The concentration of bound EDTA will therefore equal [MgY^2-]. Calculate [MgY^2-] from the mass of Mg(NO_3)_2·2H_2O and the volume of the volumetric flask. Then calculate the free [EDTA] from the equilibrium expression, and the quantity of EDTA needed from the sum of the bound and free EDTA.

© BrainMass Inc. brainmass.com October 25, 2018, 8:11 am ad1c9bdddf
https://brainmass.com/chemistry/inorganic-chemistry/chelate-with-a-metal-ion-529479

Solution Summary

Problems based on metal-EDTA titration are solved.

$2.19
See Also This Related BrainMass Solution

The nature and usefulness of metal chelates

Describe the nature and characteristics of metal chelates. Why are they of importance to an EH&S or Medical professionals who utilize them in their careers?

View Full Posting Details