Principles of Instrumental Analysis
7th Edition
ISBN: 9781305577213
Author: Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Publisher: Cengage Learning
expand_more
expand_more
format_list_bulleted
Question
Chapter 25, Problem 25.11QAP
Interpretation Introduction
Interpretation:
Scan rate at experiment 2 should be calculated.
Concept introduction:
The peak current can be represented as follows:
Here,
Ip = peak current
n = number of electrons transferred in the redox event
A = electrode surface area
C = concentration
D = diffusion coefficient
V = scan rate
Expert Solution & Answer
Want to see the full answer?
Check out a sample textbook solution
Students have asked these similar questions
How long will it take to dissolve 2 mg of metal A (atomic weight 100) in a solution
containing A2+ from a metal electrode with area of 1.5 cm2 at an overpotential of
= 0.2 V? The exchange current density (j0) for A is 3x10-3 A/cm2, the temperature
T=298 K and the symmetry factor =0.4.
6
6) Voltammetry - In linear scan voltammetry, the diffusion current is proportional to the concentration of the
species being reduced. In one experiment 250.00 mL of a 6.00 x 104 M Cd2+ (aq) solution was analyzed using
a mercury electrode. The voltammetry scan from -0.6 to -1.2 V took 3.40 minutes to complete. The diffusion
current for the reduction of Cd2+ at the mercury electrode was 14.0 μA (14.0 x 106 A).
Cd²+ (aq) + 2 e ---
-> Cd (s)
a) How many mmol Cd2+ were initially present? (in the 250.00 mL solution)
b) Using the current and time, calculate the charge (coulombs) delivered to the solution.
c) How many mmol of Cd²+ were reduced (deposited) during the analysis by this current?
d) Using the answers from parts (a) and (c), calculate the
percentage of Cd²+ that was reduced in the analysis.
e) A second solution of unknown Cd2+ concentration was analyzed similarly and the diffusion current was only
10.2 µA. What is the Cd2+ for the unknown solution? (Use current is proportional to…
Chapter 25 Solutions
Principles of Instrumental Analysis
Knowledge Booster
Similar questions
- Exactly 6.00 ml of acetic acid (density = 1.05 g/mL), MW =60.05) was added to a 1 –liter volumetric flask, and the flask was filled to the mark with distilled water. A portion of the resulting solution was added to a conductance cell (k = 1.25 cm-1), and the conductance was found to be 416 μS. Calculate the dissociation constant Ka of acetic acid. ΛoH+= 349.8 Scm2/mole and ΛoCH3COO- = 41 Scm2/molearrow_forwardAn analyst wants to find out the active surface of his electrode before conducting his analyzes. To do this, he carried out a series of measurements by cyclic voltammetry (CV) using a 1 mM solution of K4Fe(CN)6 dissolved in 0.1M NaCl. He recorded the anodic peak intensity (ip) corresponding to the oxidation of Fe(II) to Fe(III) as a function of the scanning speed (v) of the CV (see table). What is the active surface of the electrode? Data: Fe diffusion coefficient (CN)64-, D = 6.67x10-6 cm2/s Randles-Sevcik equation ip = (2,69x105)n3/2ACD1/2v1/2 rate (v/s) ip (A) 5,00E-02 5,75E-05 1,00E-01 7,68E-05 2,00E-01 9,94E-05 5,00E-01 1,42E-04 1,00E+00 2,07E-04arrow_forward[3] The following Figure is the electrocapillary curves (A) and differential capacitance curves (B) for mercury in contact with 0.5 M Na,SO4 in the presence and absence of n-heptanol . 440- (A) (B) 420 Na,So. 400 Na, So, CHOH 360 Na so, 20 340- Na So, CH,OH 10 320 0.4 0.8 12 1.6 20 24 0.4 0.8 1.2 -EV ex NCE) 1.6 2.0 -EV e NCE (a) How do the curves in figure (A) relate to those in figure (B)? (b) What implications can be derived from the flat region in the electrocapillary curves in the presence of n-heptyl alcohol? (c) If we measure the electrocapillary curve of mercury in contact with 0.5 M Na,SO4 at higher temperature, what changes in the curve can be observed? Try to give explanation of these changes.arrow_forward
- A conductivity cell when standardized with 0.01 M KCl was found to have a resistance (R) of 189 N at 25 °C. With 0.01 M ammonia solution the resistance was 2460 N at 25 °C. Calculate the base dissociation constant of ammonia by using the data tabulated in Table 1. Table 1 Molar ionic conductivities of electrolyte at infinite dilution (A.) in aqueous solution at 25 °C Cation A4,0 (Q² cm? mol1) Anion A.0 (Nª cm? mol4) NH4* 73.4 OH 198.6 K* 73.5 76.4arrow_forward4arrow_forward3) Name the errors of glass electrodes in potentiometric measurements (please write correctly and concisely).arrow_forward
- An unknown cadmium(II) solution was analyzed polarographically by the method of standard additions. A 25.00-mL sample of the unknown solution produced a diffusion current of 1.86 mA. Following addition of a 5.00-mL aliquot of 2.12x10^23 M Cd2+ standard solution to the unknown solution, a diffusion current of 5.27 mA was produced. Calculate the concentration of Cd2+ in the unknown solution.arrow_forwardDoes KMNO4 oxidize or reduce an analyte during permanganimetry?arrow_forward7. In an experiment on the Pt| Ha| H' electrode in dilute H.SO4, the following current densities were observed at 25°C. Evaluate a and I, for the electrode. n/mV 50 100 150 I/ mA cm2 200 29.9 100 250 335 2.66 8.91arrow_forward
- An unknown cadmium(II) solution was analyzed polarographically by the method of standard additions. A 26.00-mL sample of the unknown solution produced a diffusion current of 1.77 µA. Following addition of a 6.00-mL aliquot of 4.76 × 10-3 M Cd²+ standard solution to the unknown solution, a diffusion current of 5.26 µA was produced. Calculate the concentration of Cd2+ in the unknown solution. Concentration = Marrow_forwardWhat Is The Activity Coefficient Of Benzoate Ion (C7H5O2-) With An Ionic Size Parameter Of a = 0.60 nm For 0.50 M Sodium Sulfate Solution?arrow_forwardA standard addition method for the voltammetric determination of Pb2+ involved addition of 5.00 mL of 0.800 x 10-3 M Pb2+ to one of two 25.00 mL aliquots of the sample. Supporting electrolyte and water were then added to each aliquot to give a final volume of 50.00 mL. Calculate the molar concentration of Pb2+ based on the following data Diffusion current of sample only = 78.3 uA A Diffusion current of sample with standard addition = 88.7 uAarrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Principles of Instrumental AnalysisChemistryISBN:9781305577213Author:Douglas A. Skoog, F. James Holler, Stanley R. CrouchPublisher:Cengage Learning
Principles of Instrumental Analysis
Chemistry
ISBN:9781305577213
Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Publisher:Cengage Learning