Mn was used as an internal standard for measuring Fe by atomic absorption spectr

Question

Mn was used as an internal standard for measuring Fe by atomic absorption spectroscopy. A standard mixture containing 2.00 ppm and 2.50 ppm gave a Fe / Mn signal ratio (quotient) of 1.05. A 5.00 mL unknown Fe solution was mixed with 1.00 mL solution containing 12.5 ppm Mn. The absorbance of this mixture at the Mn wavelength was 0.128 and the absorbance at the Fe wavelength was 0.128. Find the concentration of the unknown Fe solution? (Note: In AAS each element is detected at its specific absorption wavelength)

Explanation / Answer

Step 1:

C1.V1=C2.V2

C=Concentration

V=Volume

Step 2:

Know Data:

C1=Mn´s concentration 12.5ppm

V1=Know Mn's volume=1.0 mL

V2= Unknown Fe´s Volume= 5.0mL

C2= Fe´s concentration=??(UNknow)

Step 3:

1.0mL Solution--------12.5ppm Mn

5.0mL Unknow Solution-----x ppm = R// 62.5ppm Fe

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