The following results were obtained when each of a series of standard silver solutions was analyzed by flame-atomic absorption spectrometry: concentration on 0 5 10 15 20 25 30 40 (ng. ml1) absorbance(r. u.) 0.003 0.127 0.251 0.390 0.498 0.625 0.763 0.771 determine the slope and intercept of the calibration plot, along with their confidence limits (95%). using the data from exercise 1 above, estimate the confidence limits for the silver concentration in: a) a sample giving an absorbance of 0.456 in a single determination. b) a sample giving absorbance values of 0.308, 0.317, 0.347, and 0.412 in four separate determinations. graph: a straight line excel plot is shown in the question

Hi. The answer are as follow:

The slope is equal to 0.0228

The coordinates of the intersection in "y" are (0,0)

The coordinates of the intersection in "x" are (0,0)

a) x = 20 ng/mL

b) x = 13.5 ng/mL

   x = 13.9 ng/mL

   x = 15.21 ng/mL

   x = 18.07 ng/mL

In the attached Excel file you can see the graph

Explanation: Graphing the data using Excel gives the attached figure. Adding the linear trend line we obtain the equation and the coefficient R. As you can see in the figure, the equation is:

y = 0.0228x

R = 0.9413

Where "y" is the absorbance and "x" the concentration. The slope is equal to 0.0228.

To calculate the intersection in “y” we must take an x = 0. Replacing in the equation would give:

y = 0.0228*(0) = 0

so when x = 0, y = 0. The coordinates of the intersection in “y” are (0,0)

To calculate the intersection in "x" we must take a y = 0. Clearing and replacing in the equation would give:

x = y/0.0228 = 0/0.0228 = 0

So when y = 0, x = 0. The coordinates of the intersection in "x" are (0,0).

a) To calculate the concentration of the sample we will use the equation of the graph. We must clear "x" which is the concentration.

x = y/0.0228 = 0.456/0.0228 = 20 ng/mL

b) We use the same procedure as part a)

x = 0.308/0.0228 = 13.5 ng/mL

x = 0.317/0.0228 = 13.9  ng/mL

x = 0.347/0.0228 = 15.21  ng/mL

x = 0.412/0.0228 = 18.07  ng/mL

Greetings

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