Chapter 13, Problem 13.143P

(a)

Interpretation Introduction

Interpretation:

The mass of caffeine that remains in the aqueous phase is to be calculated.

Concept introduction:

The distribution ratio is defined as the total concentration of a solute in the stationary phase in all possible chemical forms divided by the total concentration of a solute in the mobile phase in all possible chemical forms. It is denoted by $D$.

The formula to calculate the mass that remains in the water is as follows:

  $M_{\text{w}}=\left(f_{\text{w}}\right)\left(\text{original mass}\right)$        (1)

Here, $f_{\text{w}}$ is the fraction of substance that remains in the water.

The formula to calculate the fraction that remains in the water is as follows:

  $f_{\text{w}}=\frac{V_w}{\left(V_{\text{w}}+DV\right)}$        (2)

Here,

$V_w$ is the volume of the water.

$V$ is the volume of a substance.

$D$ is the distribution ratio for the solubility.

(b)

Interpretation Introduction

Interpretation:

The mass of caffeine that remains in the aqueous phase after each extraction in two successive extractions is to be calculated.

Concept introduction:

The distribution ratio is defined as the total concentration of a solute in the stationary phase in all possible chemical forms divided by the total concentration of a solute in the mobile phase in all possible chemical forms. It is denoted by $D$.

The formula to calculate the mass that remains in the water is as follows:

  $M_{\text{w}}=\left(f_{\text{w}}\right)\left(\text{original mass}\right)$        (1)

Here, $f_{\text{w}}$ is the fraction of substance that remains in the water.

The formula to calculate the fraction that remains in the water is as follows:

  $f_{\text{w}}=\frac{V_w}{\left(V_{\text{w}}+DV\right)}$        (2)

Here,

$V_w$ is the volume of the water.

$V$ is the volume of a substance.

$D$ is the distribution ratio for the solubility.

(c)

Interpretation Introduction

Interpretation:

The approach that extracts more caffeine is to be determined.

Concept introduction:

The solvent extraction is a technique to separate compounds on the basis of their relative solubilities in two different immiscible liquids. One of the liquids is generally water (polar) and the other one is an organic solvent (non-polar). This method is used in extraction that is carried out in hydrometallurgy, wastewater treatment, biochemistry, nuclear chemistry, pharmaceutical industry, and mass spectroscopy.