Question

At what pH does ${\mathit{\alpha }}_{{\mathbf{y}}^{\mathbf{4}\mathbf{-}}}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{50}$?

Short answer

At pH 10.35 the value of ${\alpha }_{{\mathrm{y}}^{4-}}=0.50$

Step-by-step solution

Introduction

The fraction of all free EDTA (in Y^4- format) is expressed in terms of ${\alpha }_{Y^{4-}}$. It can be expressed as

${\alpha }_{Y^{4-}}=\frac{\left[Y^{4-}\right]}{\left[H_6{Y}^{2+}\right]+\left[H_5{Y}^{+}\right]+\left[H_{4}Y\right]+\left[H_3{Y}^{-}\right]+\left[H_2{Y}^{2-}\right]+\left[H{Y}^{3-}\right]+\left[Y^{4-}\right]}$

Given Data

In table 12-1 values of for EDTA at different pH is given.

From the above table the following graph was obtained