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
