Chapter 14, Problem 14.1QAP

Interpretation Introduction

Interpretation:

The concentration of the quinine present in the sample to be calculated.

Concept introduction:

The absorbance of a solution is basically it’s ability to absorb the intensity of the light incident.

The change in the concentration of the solution brings about the change in the absorbance of the solution.

The change in the concentration required for the particular change in absorbance is given by:

  $c_x=\frac{A_1{c}_s{V}_s}{\left(A_2-A_1\right)V_x}$

Answer to Problem 14.1QAP

The concentration of the quinine solution is $22.0\text{ppm}$ .

Explanation of Solution

The expression for the concentration of the quinine is:

  $c_x=\frac{A_1{c}_s{V}_s}{\left(A_2-A_1\right)V_x}$ ..... (1)

Where,

• $c_x$ is the unknown concentration of quinine.
• $c_s$ is the known concentration of the solution.
• $A_1$ is the absorbance of the quinine solution for unknown concentration.
• $A_2$ is the absorbance of the quinine solution for known concentration.
• $V_x$ is the volume of the unknown solution.
• $V_s$ is the variable volume of solution.

The value of $A_1$ is $0.636$ .

The value of $c_s$ is $23.1\text{ppm}$ .

The value of $V_{\text{s}}$ is $10.0\text{ml}$ .

The value of $A_2$ is $0.903$ .

The value of $V_x$ is $25.0\text{ml}$ .

Substitute the values in equation (1).

  $\begin{array}{c}{c}_x=\frac{A_1{c}_s{V}_s}{\left(A_2-A_1\right)V_x}\\ c_x=\frac{\left(0.636\right)\left(23.1\text{ppm}\right)\left(10.0\text{ml}\right)}{\left(0.903-0.636\right)\left(25.0\text{ml}\right)}\\ =\frac{146.916}{6.675}\text{ppm}\\ \approx \text{22}\text{.0}\text{ppm}\end{array}$

The concentration of the quinine solution is $22.0\text{ppm}$ .

Conclusion

Thus, the concentration of the quinine solution is $22.0\text{ppm}$ .