Question

1. Check Beer's Law by plotting absorbance vs molar concentration using 2. Is Beer's Law valid for this system? Explain your answer. 3. If Beer's Law is valid, the value of "E" should be constant. Use A-ECPL or E = A/(EL) and the data from Table II to calculate values of E for the five solutions below. The value of L is normally 1 cm so E - A/C in this experiment. Table III Solution # Calculated Values of E 2 w Concentration of unknowns found from graph: Unknown #_ _concentration value _% error Absorbance value Reference Unknown # Absorbance value Reference _concentration % error value

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Answer 1

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As you can see, the plot between absorbance and molar concentration is giving a linear plot, it obeys the Beer's law which says A-E*C*L where, E is molar extinction coefficient, C is concentration and L is path length. 1.2 B No Weighing 0.052030.0460 2.024670.1514 9.91032 Weight Intercept Slape Residual Sum af Square Pearsar's r RSquare (COD) Adj R-Square 1.0 0.99171 0.8 As it is also given that L is 1 cm. So when we plot A vs. C plot, the slope will be E. From our plot, we get slope is 2.024. thus E is 2.024 0.98349 0.97799 0.6 0.4 Now if we write the equation to calculate the unknown concentrations, we must write A-(2.024*C+0.052 Now, unknown concentrationC1 and C2 and corresponding absorptions are A1-0.752 and A2-0.188 respectively. Thus C1=(0.752-0.052)/2.024 0.345 M And C2=(0.188-0.052)/2.024 0.0672 M 0.2 0.0 0.0 0.1 02 03 04 0.5 Concentration, M Absorbance