Question

Table 1. Beer's Law data for curcumin standards at $\lambda_{max}$. Concentration (M) Absorbance ($\lambda_{max}$) 4.00E-05 1.77 2.00E-05 1.13 1.50E-05 0.87 1.00E-05 0.59 5.00E-06 0.38 a. Plot the data points given in the table on the following graph. Use a ruler to draw a best-fit line. Calibration Curve for Curcumin b. Calculate the extinction coefficient for curcumin from the slope of your graph and explain its significance. Assume a path length of 1 cm. c. Your lab partner brings you another sample at a concentration of 5.00$\times10^{-5}$ M. You record the absorbance and the instrument reads 2.15. Do you think you should include this data in your plot and resolve for the slope? Why or why not? d. Suppose you conduct an extraction of curcumin from grated turmeric root. You record a spectrum of your sample, and the resulting absorbance value is 0.80 at $\lambda_{max}$. What is the concentration of your extraction sample? e. The sample you used in part d was actually diluted before you determined its absorbance at $\lambda_{max}$. If you took 1.0 mL of your extraction and diluted it in 5.0 mL of ethanol before taking the absorbance measurement, what was the original concentration of your extraction?

          Table 1. Beer's Law data for curcumin standards at $\lambda_{max}$.
Concentration (M)	Absorbance ($\lambda_{max}$)
4.00E-05	1.77
2.00E-05	1.13
1.50E-05	0.87
1.00E-05	0.59
5.00E-06	0.38
a. Plot the data points given in the table on the following graph. Use a ruler to draw a best-fit
line.
Calibration Curve for Curcumin
b. Calculate the extinction coefficient for curcumin from the slope of your graph and explain
its significance. Assume a path length of 1 cm.
c. Your lab partner brings you another sample at a concentration of 5.00$\times10^{-5}$ M. You record
the absorbance and the instrument reads 2.15. Do you think you should include this data
in your plot and resolve for the slope? Why or why not?
d. Suppose you conduct an extraction of curcumin from grated turmeric root. You record a
spectrum of your sample, and the resulting absorbance value is 0.80 at $\lambda_{max}$. What is the
concentration of your extraction sample?
e. The sample you used in part d was actually diluted before you determined its absorbance
at $\lambda_{max}$. If you took 1.0 mL of your extraction and diluted it in 5.0 mL of ethanol before
taking the absorbance measurement, what was the original concentration of your
extraction?

Table 1. Beer's Law data for curcumin standards at λmax.
Concentration (M) Absorbance (λmax)
4.00E-05 1.77
2.00E-05 1.13
1.50E-05 0.87
1.00E-05 0.59
5.00E-06 0.38
a. Plot the data points given in the table on the following graph. Use a ruler to draw a best-fit
line.
Calibration Curve for Curcumin
b. Calculate the extinction coefficient for curcumin from the slope of your graph and explain
its significance. Assume a path length of 1 cm.
c. Your lab partner brings you another sample at a concentration of 5.00×10^-5 M. You record
the absorbance and the instrument reads 2.15. Do you think you should include this data
in your plot and resolve for the slope? Why or why not?
d. Suppose you conduct an extraction of curcumin from grated turmeric root. You record a
spectrum of your sample, and the resulting absorbance value is 0.80 at λmax. What is the
concentration of your extraction sample?
e. The sample you used in part d was actually diluted before you determined its absorbance
at λmax. If you took 1.0 mL of your extraction and diluted it in 5.0 mL of ethanol before
taking the absorbance measurement, what was the original concentration of your
extraction?

Added by Darlene W.

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