Question

In this experiment, a calibration curve, often called a Beer's Law plot, will be made. A calibration curve should have which of the following attributes? (Select all that apply.)A. Absorbance is plotted on the x-axis.B. Concentration is plotted on the x-axis.C. The x- and y-axes should be labeled with units as well as quantities.D. Concentration is plotted on the y-axis.E. In a hand-plotted graph, individual lines should be drawn between adjacent points.F. Absorbance is plotted on the y-axis.G. The command for getting an equation is "Add Trendline" in Microsoft Excel.

Answer 1

Answer:

B, C  and F are true, see explanation below.

Explanation:

Beer´s law is given by the formula:

A = εcl,  where   A = Absorbance,

                           ε = molar extinction coefficient,

                           c = concentration in mol/L (M), and

                           l = path length of the cuvette containing the sample,

                               

Now the usefulness of this relation is that if we plot the Absorbance vs  concentration, we get a straight line since the Beer equation has the form  y = mx + b.After the slope and y intercept have been determined, we can determine an unknow concentration of the substance by measuring its absorbance.

This relation is valid for low concentration, and  there are deviations from it.

We are now ready to answer this question with this brief introduction:

A. Absorbance is plotted on the x-axis

False, we plot the absorbance in the y-axis.

B. Concentration is plotted on the x-axis.

True, we vary the concentration and read the absorbance so the plot is Absorbance vs Concentration.

C. The x- and y-axes should be labeled with units as well as quantities

This is true for our plot to be useful and correct.

D. Concentration is plotted on the y-axis

False, for all the reasons stated above.

E. In a hand-plotted graph, individual lines should be drawn between adjacent points

False, in a hand plotted graph we will pass the line between all the points determined as close as to produce the best line where we can read values for the absorbance for a given concentration.

F. Absorbance is plotted on the y-axis

True

G. The command for getting an equation is "Add Trendline" in Microsoft Excel.

False, the command adds only the line of the best fit to our data, to get the equation of the line we have to specify it by choosing it in the options for the format of trendline.