Print Calculator Periodic Table stion 7 of 13 Atomic absorption spectrometry was

Question

Print Calculator Periodic Table stion 7 of 13 Atomic absorption spectrometry was used with the method of standard additions to determine the concentration of cadmium in a sample of an industrial waste stream. For the addition, 100 of a 1000. giml Cd standard was added to 100 ml of solution. The follawing data were obtained: rbance of reagent blank 0.036 Absorbance of sample 0.357 Absorbance of sample plus addition 0.712 What was the concentration of the cadmium in the waste stream sample? Number /mL Later, the analyst learned that the blank was not truly a reagent blank, but water. The absorbance of the blank / ml, Calculate the percent error caused by using water instead of the reagent blank Number Previous Gold Up & View Salutin D Check Answer () Next Hint FS F8 F10 8 7 5

Explanation / Answer

Estimation of Cd in waste water stream sample

Standard addition method

standard added = 10 uL (0.01 ml) of 1000 ug/ml

Concentration of standard Cd in solution after addiiton (Cs) = 1000 ug/ml x 0.01 ml/10.01 ml = 0.999 ug/ml

let concentration of Cd in waste stream be Cx

Absorbance due to sample (As) = 0.357 - 0.036 = 0.321

Absorbance due to sample + standard (A) = 0.712 - 0.036 = 0.676

Using,

Cx/(Cx + Cs) = As/A

Feeding values,

Cx/(Cx + 0.999) = 0.321/0.676

Cx = 0.9033 ug/ml

so, the concentration of Cd in waste stream = 0.9033 ug/ml

---

Now, the reagent blank was not true blank,

the true blank had an absorbance = 0.076

So new values would be,

Absorbance due to sample (As) = 0.357 - 0.076 = 0.281

Absorbance due to sample + standard (A) = 0.712 - 0.076 = 0.636

Using,

Cx/(Cx + Cs) = As/A

Feeding values,

Cx/(Cx + 0.999) = 0.281/0.636

Cx = 0.791 ug/ml

so, the concentration of Cd in waste stream = 0.791 ug/ml

--

Percent error due to use of water instead of reagent blank

= (0.9033 - 0.791) x 100/0.791 = 14.20%

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.