Description
Mn=internal standard to measure Fe by Atomic Absorption.
ug= micrograms
Standard mixture: 2 ug Mn/mL & 2.50 ug Fe/mL gave quotient (signal?) of 1.05/1.00. A mixture with a volume of 6 mL was prepared by mixing 5 mL of unknown Fe solutionn w/1 mL containing 13.5 ug Mn/mL.
Absorbance of Mn: 0.128
Absorbance of Fe: 0.185
Find the molarity of the Unknown Fe solution.
Explanation & Answer
Airon=(Kiron)(Ciron)
Amn=(Kmn)(Cmn)
Airon/Amn= 1.05 = (Kiron)(2.50) / (Kmn)(2.00)
Kiron/Kmn = 0.84
(Kiron)(Ciron) =0.370
(Kmn)(13.5/6)=0.128
Divide the top equation by the bottom one:
2.891 = (Kiron / Kmn)*(Ciron / 2.25) = (0.84)*(Ciron / 2.25)
Ciron(after mixing) = 7.743 mg/L
Ciron(actual) = 7.743*(6/5) = 9.29 mg/L
9.29 mg/L * (1 g / 1000 mg) / (55.8 g/mol) = 1.66 * 10^-4 M
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