The calibration curve between absorbance and concentration of standard series should be plotted. Using the regression line & the plot the concentration of the unknown solution should be calculated. The accuracy of these 2 methods should be compared by considering the final answers.Error analysis of the data should be done. Concept introduction: The absorbance of light can be determined by the Beer-Lambert law. The chemical equation relevant to the law is, A = c l ε Where, A = Absorbance c = Concentration of the solution l = Path length of the cell ε = Absorptivity of the solution Standard deviation of a data series can be calculated by the following equation. ( Σ i = 1 N x i 2 ) − ( Σ i = 1 N x ) N N − 1 2

Question

A compound X is to be determined by UV-visible spectrophotometry. A calibration curve is constructed from standard solutions of X with the following results: 0.50 ppm, A = 0.24; 1.5 ppm, A = 0.36; 2.5 ppm, A = 0.44; 3.5 ppm, A = 0.59; 4.5 ppm, A = 0.70. A solution of unknown X concentration had an absorbance of A = 0.50. Find the slope and in te rcept of the calibration curve, the standard error in Y, the concentration of the solution of unknown X concentrat ion, and the standard deviation in the concentration of X. Construct a plot of the calibration curve and determine the unknown concentra tion by hand from the plot. Compare it to that obtained from the regression line.

Answer 1

Question

Chapter 13, Problem 13.26QAP

Interpretation Introduction

Interpretation:

The calibration curve between absorbance and concentration of standard series should be plotted. Using the regression line & the plot the concentration of the unknown solution should be calculated. The accuracy of these 2 methods should be compared by considering the final answers.Error analysis of the data should be done.

Concept introduction:

The absorbance of light can be determined by the Beer-Lambert law. The chemical equation relevant to the law is,

A=clε

Where,

A = Absorbance

c = Concentration of the solution

l = Path length of the cell

ε = Absorptivity of the solution

Standard deviation of a data series can be calculated by the following equation.

(Σi=1Nxi2)−(Σi=1Nx)NN−12

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