# Electrochemistry Homework Problem Set #3

This problem set was developed by S.E. Van Bramer for Chemistry 366 at Widener University.

Questions are based on Skoog, West & Holler An Introduction to Analytical Chemistry. Some questions and data are based upon information from this textbook.

1. (3 pts) Compare and contrast the instrument settings, the sensitivity, and the signal for the following electrochemical techniques.
1. Linear-scan vs normal pulse voltammetry
2. Normal pulse vs differential pulse voltammetry
3. Differential pulse vs square wave voltammetry
4. Anodic stripping voltammetry vs voltammetry

2. (3 pts) What would you do if....
1. You are running a differential pulse experiment with pulse width of 1 ms and a pulse height of 100 mV and a glassy carbon electrode. What would you do to increase the S/N.
2. You are running a differential pulse experiment with pulse width of 1 ms and a pulse height of 100 mV and a glassy carbon electrode. What would you do to improve the resolution.
3. You are running a normal pulse experiment with pulse width of 20 ms and a glassy carbon electrode. What would you do to improve the resolution.
4. You are running a square wave experiment with a 1 kHz pulse frequency and a dropping mercury electrode. What would you do to significantly reduce the limit of detection.

3. (4 pts) An unknown sample was analyzed by differential pulse voltammetry with a DME. Samples were prepared by pipetting (with Class A pipetts) the volumes indicated and diluting to a total volume of 50.00 mL in a Class A volumetric flask. The following samples were prepared and analyzed. Calculate the concentration of lead in the original sample. Use propagation of error to determine the uncertainty in the concentration.
 Sample (mL) KCl (mL) 0.400 M Pb2+ (mL) 12.4 ppm Current (uA) 20.00 10.00 0 46.48 20.00 10.00 0 46.36 20.00 10.00 0 46.46 20.00 10.00 0 46.22 20.00 10.00 0 46.7 20.00 10.00 1.00 51.32 20.00 10.00 1.00 51.24 20.00 10.00 1.00 51.58 20.00 10.00 1.00 51.40