Question

The figure shows a series of standard additions of Cu?+ to acidified tap water measured by anodic stripping voltammetry at an iridium electrode. The unknown and all standard additions were made up to the same final volume. 2.0 + 500 ppb +400 ppb 1.6 + 300 ppb +200 ppb 1.2 Current (A) + 100 ppb 0.8 Tap water 0.4 0.1 0.2 0.3 0.4 Potential (V vs. Ag | AgCl) Anodic stripping voltammograms of tap water and five standard additions of 100 ppb Cu2+ [Data from M. A. Nolan and S.P. Kounaves, "Microfabricated Array of Ir Microdisks for Determination of Cu2+ and Hg2+ Using Square Wave Stripping Voltammetry," Anal. Chem. 1999, 71, 3567.) What chemical reaction occurs during the concentration stage of the analysis? reaction: Incorrect What chemical reaction occurs during the stripping stage of analysis? reaction: Incorrect Measure the initial current and the current after each standard addition and find the concentration of Cu2+ in the tap water. [Cu²+1 = 173.33 ppb Incorrect

complete question

Answer 1

(a) Concentration (deposition) stage: Cu^​​​2+ + 2e~ —> Cu(,s')

(b) Stripping stage: Cu(.v) – Cu^{​​​​​2+} + 2e~

(c) All solutions were made up to the same volume, so [X]i = [X]f = x. Prepare a graph of/vs. [S]f using data measured from the figure in the problem. The intercept is at-313 ppb, so the original concentration of Cu^​​​2+ is 313 ppb.

Added standard (ppb) 0 100 200 300 400 500 Current (UA) 0.599 0.774 0.943 1.128 1.314 1.544 1.6 1.4 1.2. 1.0 Current (UA) 0.8 y = 0.001 866 x + 0.5839 Intercept -313 ppb 0.6 0.4 0.2 -300 -200 -100 0 100 400 500 200 300 (S): (ppb)