Chapter 14, Problem 14.17QAP

Interpretation Introduction

(a)

Interpretation:

The formula of the complex should be determined.

Concept introduction:

Slope-ratio method is used for weak complexes,

$x\text{M + }y\text{L }\rightleftharpoons {\text{ M}}_x{\text{L}}_y$

When L is in excess, $C_M=x\left[{\text{M}}_x{\text{L}}_y\right]$

$A_1=\epsilon l\left[{\text{M}}_x{\text{L}}_y\right]=\epsilon l\frac{C_M}{x}$

When M is in excess, $C_L=y\left[{\text{M}}_x{\text{L}}_y\right]$

$A_2=\epsilon l\left[{\text{M}}_x{\text{L}}_y\right]=\epsilon l\frac{C_L}{y}$

Therefore slope of the plot of absorbance versus concentration of M or L gives $\frac{\epsilon l}{x}$ or $\frac{\epsilon l}{y}$ respectively.

The ratio of the two slope will give the combining ratio of M and L.

$\frac{\epsilon l/x}{\epsilon l/y}=\frac{y}{x}$

Interpretation Introduction

(b)

Interpretation:

The molar absorptivity of the complex and its uncertainty should be determined.

Concept introduction:

Slope-ratio method is used for weak complexes,

$x\text{M + }y\text{L }\rightleftharpoons {\text{ M}}_x{\text{L}}_y$

When L is in excess, $C_M=x\left[{\text{M}}_x{\text{L}}_y\right]$

$A_1=\epsilon l\left[{\text{M}}_x{\text{L}}_y\right]=\epsilon l\frac{C_M}{x}$

When M is in excess, $C_L=y\left[{\text{M}}_x{\text{L}}_y\right]$

$A_2=\epsilon l\left[{\text{M}}_x{\text{L}}_y\right]=\epsilon l\frac{C_L}{y}$

Therefore slope of the plot of absorbance versus concentration of M or L gives $\frac{\epsilon l}{x}$ or $\frac{\epsilon l}{y}$ respectively.

The ratio of the two slope will give the combining ratio of M and L.

$\frac{\epsilon l/x}{\epsilon l/y}=\frac{y}{x}$