Respuesta :
Explanation:
According to the Beer-lambert' s law,
Absrobance = absrobptitvity × lenght × concentration
So, if we will plot a graph between absrobance and concentration then we will obtain a straight line
Hence, formula to calculate slope of the graph is as follows.
The slope of graph = [tex]\frac{\text{difference in absrobance at two points}}{\text{difference in concentrations at those points}}[/tex]
The given data is as follows.
[tex]A_{1}[/tex] = 0.412 (first point)
[tex]A_{2}[/tex] = 0.642 (second point)
[tex]C_{1}[/tex] = 0.240 ppm (first point)
[tex]C_{2}[/tex] = 0.475 ppm (second point)
Hence, putting these values into the above formula we will calculate the value of slope as follows.
Slope = [tex]\frac{\text{difference in absrobance at two points}}{\text{difference in concentrations at those points}}[/tex]
= [tex]\frac{0.642 - 0.412}{0.475 - 0.240}[/tex]
= [tex]\frac{0.23}{0.235}[/tex]
= 0.978
It is known that for the graph, line equation can be written as follows.
y = mx + c ........... (1)
where, C = intercept
m = slope
Hence, calculate the value of intercept as follows.
0.412 = [tex]0.24 \times 0.978[/tex] + c
c = 0.178
As it is given that the absorbance values 0.454 (the y-axis value). Therefore, putting this value into equation (1) we get the following.
y = mx + c
0.454 = [tex]x \times 0.978[/tex] + 0.178
0.276 = 0.978x
x = 0.282 ppm
Thus, we can conclude that the concentration of Pb in the given sample is 0.282 ppm.
