Chapter 1, Problem 1.11QAP

Interpretation Introduction

(a)

Interpretation:

A standard-addition plot should be created using the data given.

Concept introduction:

A commonform of standard-addition method involves adding known amounts of a standard solution to sample aliquots containing a fixed volume. Measurements taken for each solution can be used to plot a standard-addition plot.

Interpretation Introduction

(b)

Interpretation:

Using the standard-addition plot constructed, the concentration of the unknown phenobarbital sample should be determined.

Concept introduction:

In a standard-addition plot, the graph can be extrapolated to obtain thevolume of standard reagentequivalent to the amount of analyte in the sample ( ${(V_s)}_0$ ). This value can be used in the following equation to calculate the concentration ( $C_x$ ) of the unknown sample.

$C_x=-\frac{{(V_s)}_0{C}_s}{V_x}$

Where,

$C_s$ = concentration of the standard

$V_x$ = constant volume of the unknown added to each sample solution.