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.

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.

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter25: Voltammetry

Section: Chapter Questions

Problem 25.13QAP

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An unknown cadmium(II) solution was analyzed. 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 0.00212 M Cd2+ standard solution to the unknown solution, a diffusion current of 5.27 mA was produced. A) What type of electroanalytical method was used? B) What type of calibration method was used? C) What is the molar concentration of Cd2+ in the unknown solution?
An ion selective electrode is utilised to determine the concentration of Ca2+ in the presence of Mg2+. The selectivity coefficient for the electrode kij is 0.015. If the concentrations of Ca2+ and Mg2+ are 50 and 500 ppm, respectively, calculate the change in potential (in mV) when the temperature of the measurement cell is increased from 20oC to 40oC.
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A conductivity cell was calibrated using 0.01 M KCl (κ = 1.4087x10-3 S/cm) and the measured resistance was 688 Ω. a. Determine the cell constant (include units). b. Determine the molar conductivity, Λm for a 0.0100 M AgNO3 solution in the same cell with a resistance reading of 777Ω.
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A 0.2g sample of toothpaste containing fluoride was treated with 50 cm3 of a suitable buffer solution and diluted to 100 cm3. Using a fluoride ion-selective electrode, a 25.00 cm3 aliquot of this solution gave cell potentials of –155.3 mV before and –176.2 mV after spiking with 0.1 cm3 of a 0.5 mg/cm3 fluoride standard. Calculate the pF– corresponding to each cell potential and the percentage by weight of fluoride in the toothpaste.
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A 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 uA
When a certain electrolytic cell was filled with 0.1 M KC1, it has resistance of 85 ohms at 25 °C. When the same cell was filled with an aqueous solution of 0.052 M unknown electrolyte, the resistance was 96 ohms. Calculate the molar conductance of the electrolyte at this concentration.[Specific conductance of 0.1 M KC1 = 1.29 X 10-2ohm-1 cm-1]