please answer the follwing questions 2-A water sample was run through the colori

Question

please answer the follwing questions

2-A water sample was run through the colorimetric procedure for the analysis of nitrate, giving 55.0% transmittance. A sample containing 1.00 ppm nitrate run through the exactly identical procedure gave 24.6% transmittance. What was the concentration of nitrate in the first sample?

3-Analysis of a leadcontaining sample by graphitefurnace atomic absorption analysis gave a peak of 0.075 absorbance units when 50uL of pure sample was injected. Lead was added to the sample such that the added concentration of lead was 6.0ug/L. Injection of 50uL of ‘spiked’ sample gave an absorbance of 0.115 absorbance units. What was the concentration of lead in the original sample?

Explanation / Answer

The relation between absorbance and transmittance is given by A= 2-log (%T)

55% transmittance correspond to A= 2-log (55)= 0.2596

for 24.6% tranasmittance A= -log (24.6)= 0.6091

but absorance A= ebc

for A= 0.2596 = ebc ( e and b are constant s

A= 0.6091 =ebC1

C1/C= 0.6091/0.2596

C1=2.34 ppm

3. from A = ebc ( eb are constants)

0.075= ebC1 ( C1 is concentration of lead pure sample)

0.11 =ebC2   

C2/C1=0.11/0.075=1.46

C2=6*1.46 =8.76 ug/L

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