Aqueous Ni^2+ absorbs visible light with a lambda_max of approximately Use the d

Question

Aqueous Ni^2+ absorbs visible light with a lambda_max of approximately Use the data in the following Beer's Law plot to answer the following If a sample of water containing Ni^2+ has an absorbance measure to the 0.078 at 635 nm, what is the concentration of nickel ions in the solution? A sample of metal alloy containing iron, nickel and chromium is dissolved in nitric acid forming aqueous Fe^3+, Ni^2+ and Cr^3+ ions. A sample of the alloy weighs 0.1257 grams and is dissolved in 100.00 mL of nitric acid. The Absorbance of this solution at 635 nm is measured to be 1.006. How many moles of nickel were in the sample of alloy? Assume that that iron and chromium ions do NOT absorb significantly at 635 nm.

Explanation / Answer

A. y = mx+ c

y = 0.0135x + 0.0123

y = Absorbance = 0.078

So, 0.078 = 0.1135x + 0.0123

x = 0.579M = conc of Ni2+ ions

B. y = 0.1135x + 0.0123

1.006 = 0.1135x + 0.0123

x = conc of Ni2+ = 8.755M

moles = molarity x volume in liters = 87.55 x 0.1 L = 0.87 moles

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