A drinking water supply is suspected of being contaminated with lead. Samples of water aspirated directly into an air-acetylene flame gave an absorbance of 0.68 at 283.3nm. Standard solutions containing 0.5 and 1.0 ppm were found to exhibit absorbances of 0.43 and 0.86 respectively. Assuming the Beer-Lambert law is obeyed calculate the concentration of lead within the water sample. A. 79. Oppm B. 0.79ppm C. 0.43ppm D. 0.96ppm E. 0.92ppm noeullib noilgoeps noods Whaooah

Question

Chemistry

Jethro

26 January, 15:50

A drinking water supply is suspected of being contaminated with lead. Samples of water aspirated directly into an air-acetylene flame gave an absorbance of 0.68 at 283.3nm. Standard solutions containing 0.5 and 1.0 ppm were found to exhibit absorbances of 0.43 and 0.86 respectively. Assuming the Beer-Lambert law is obeyed calculate the concentration of lead within the water sample. A. 79. Oppm B. 0.79ppm C. 0.43ppm D. 0.96ppm E. 0.92ppm noeullib noilgoeps noods Whaooah

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Jonathan Bolton · Answer 1

B. 0.79ppm

Explanation:

According to the Beer-Lambert law, there is a linear relationship between the absorbance (A) of an analyte and its concentration (c). We can represent it through the following expression.

A = k. c

where

k is a proportionality constant, and the slope of the equation.

Let's consider the ordered-pairs (0.5 ppm, 0.43) and (1.0 ppm, 0.86). The slope is:

k = ΔA / Δc = 0.86 - 0.43 / 1.0 ppm - 0.5 ppm = 0.86 ppm⁻¹

When A = 0.68

0.68 = 0.86 ppm⁻¹ c

c = 0.79 ppm