A spectrophotometric study of copper(II) ions in aqueous solution was conducted.

Question

A spectrophotometric study of copper(II) ions in aqueous solution was conducted. The absorbance of a series of solutions of known concentrations of copper(II) ions was measured at 645nm, and a plot of absorbance (y-axis) vs. concentration (x-axis) was constructed. The equation for the best fit line obtained was y=13.0x+0.011. The absorbance of a solution of unknown concentration of copper(II) ions was then determined to be 0.348. What is the concentration of copper(II) ions in this solution?

A. 0.011 M
B. 0.0259 M
C. 0.0276 M
D. 0.348 M
E. 4.54 M

Explanation / Answer

Given that absorbance = 0.348

              y = 13.0x + 0.011 where y = concentration and x = concentration

         0.348 = 13.0x + 0.011

          x = 0.337 /13

            = 0.0259 M

       x = 0.0259 M

Therefore,

concentration of copper(II) ions = 0.0259 M

Ans = B

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