Question

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

Answer 1

Answer:

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