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In: Chemistry

The magnesium in a series of soil samples was characterized by atomic absorption spectrometry (AAS). The...

The magnesium in a series of soil samples was characterized by atomic absorption spectrometry (AAS). The instrument was calibrated with a series of standards: 0, 50.00, 100.00, 250.00 mg/L MgSO47H2O. These samples produced average instrument readings of 0.005; 0.192 ; 0.401 ; and 0.993. Triplicate analysis of an unknown yielded instrument readings of 0.328, 0.340, 0.335. What is the average concentration and standard deviation of the unknown? Report your answer as ppm Mg. THE OPTION IS NOT 211

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Expert Solution

The average concentration is

0.328 + 0.340 + 0.335 = 1.003/3

                                    = 0.334 ppm

Standard deviation
standard deviation =

where, xi is the individual value from population

            n is the number of population

            is the population mean

(xi-)2 = (0.328 - 0.334)2 = (0.006)2 = 0.000036

               (0.340 - 0.334)2 = (0.006)2 = 0.000036

               (0.335 - 0.334)2 = (0.001)2 = 0.00001

      S.D.             = [0.000082/3]1/2

                          = [2.73 x 10-5]1/2

   S.D. = 0.005228 ppm

queen_honey_blossom answered 1 year ago
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