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 × 10-8 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 M

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 × 10-8 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 M

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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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.
Zinc is to be used as an internal standard for the polarographic analysis of thallium. A standard solution containing twice the concentration of zinc as Thallium has a diffusion current of 1.89 µA for Ti and 3.50 µA for Zn. A 10.0g alloy was dissolved in 500 mL, 25 mL of this solution was mixed with 25 mL of 1.0 x 10-3 M Zn 2+ solution. The diffusion currents of this final solution are 18.2µA for Tl+ and 14.5µA for Zn+. Calculate % Ti in the sample analysed
An 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-04
The exchange current density at the electrode Pt| Fe3+| Fe2+ is 2.4 x 10-3 A cm-2, How many electrons are transported through the double layer per second in the cell (area of 1 cm2 each)? Estimate the number of times per second that a single atom on the surface takes part in an electron transfer event, assuming that the atom occupies 280 pm2 of the surface of the electrode.
The resistances of a series of aqueous NaCI solutions, formed by successive dilution of a sample, were measured in a cell with cell constant (the constant C in the relation κ = C/R) equal to 0.2063 cm-1. The following values were found: c/(mol dm-3) 0.00050 0.0010 0.0050 0.010 0.020 0.050R/Ω 3314 1669 342.1 172.5 89.08 3714(a) Verify that the molar conductivity follows the Kohlrausch law and find the limiting molar conductivity. (b) Determine the coefficient κ, (c) Use the value of κ (which should depend only on the nature, not the identity of the ions) and the information that λ(Na+) = 5.01 mS m2 mol-1 and , λ(I-) = 768 mS m2 mol-1, to predict (i) the molar conductivity, (ii) the conductivity,(iii) the resistance it would show in the cell, of 0.010 mol dm-3 Nal(aq) at 25 °C.
The resistance of a decinormal solution of a salt occupying a volume between Pt electrodes is 1.80 cm apart and 5.4 cm2 in area was found to be 32 ohms. Calculate the equivalent conductance of the solution.
The transfer coefficient of a certain electrode in contact with M2+ and M3+ in aqueous solution at 25 °C is 0.42. The current density is found to be 17.0 mA cm2 when the overpotential is 105 mV. What is the overpotential required for a current density of 72 mA cm−2? Hint: See hint to Exercise E19D.1(a).
In a moving boundary experiment with 0.1N KCI using 0.005N LICI, as indicator solution, a constant current of 0.005893 amp was passed for 2130 seconds and the boundary was observed to move through 5.6cm in a tube of 0.1142 sq.cm. .cross-section. Calculate the transport number of K+ and CI – ions .a t- = 0.492, t+ =0.508 t+ = 0.402, t- =0.598 .b O .c O t+ = 0.492, t- =0.508 .d O t+ = 0.402, t- =0.598
When the transport of the 0,05moldm' KCI aqueous solution was measured at 25°C using the interfacial transfer method, the interface with the CdCl2 aqueous solution moved by 6.3cm for 30 minutes. The current flowing was 0.0052 A and the cross-sectional area of the tube was 0.15 cm이었다. Find the carrying rate of K+?
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…
Cyclic voltammetry was used to measure the peak current at several different scan rates for the reversible reaction Sn(IV) → Sn(II) of an organic tin-containing complex. The concentration of the reactant is 4.96 mM and the area of the working electrode is 0.0250 cm². Calculate the diffusion coefficient of the reactant for this two-electron reduction. D = 1.03 ×10-5 Incorrect m²/s Scan Rate (V/s) 0.0135 0.0279 0.0538 0.0951 0.149 0.201 0.274 Peak Cathodic Current (μA) 4.12 5.48 7.70 9.87 12.52 14.91 17.59
The exchange-current density for a Pt|Fe3+,Fe2+ electrode is 2.5 mA cm−2. The standard potential of the electrode is +0.77 V. Derive an expression for the current flowing through an electrode of surface area 1.0 cm2 as a function of the potential applied to the electrode; assume standard conditions.