What Is the Cell Potential for The Galvanic Cell Exam Practice

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The last page of the exam contains a selection of data tables and equations for your use – feel free to remove the page from the exam.































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  1. (10 points) What is the cell potential for the galvanic cell described by the line notation below?

Mg(s) | Mg(OH)+ (45.92 mM), pH = 6.05 || IrCl62– (15.47 mM), Cl– (9.02 mM) | Ir(s)

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  1. (5 points) Write out the Beer’s law equation and identify all the variables.





𝞮 = molar absorptivity (1/M•cm)


        1. = path length (cm)
        2. = molar concentration (M)




  1. (5 points) For the following questions consider the three principle types of spectrometers that are used for analyses: flame, graphite furnace, and inductively coupled plasma (ICP). For each question select the best system:

        1. Which instrument is capable of analyzing solids?


 Graphite furnace


        1. Which instrument reaches the highest temperatures?




        1. Which instrument has the longest path length?


Flame spectrometer


        1. Which is best for atomic emission spectroscopy?




        1. Which can execute a programed temperature cycle?

Graphite furnace

  1. (10 points) A tin (Sn) metal indicator electrode is being used to determine the concentration of sulfide (S2–) in an unknown solution. The measurement is done by mixing a known tin nitrate (Sn(NO3)2) solution with some of the sulfide solution (details below) and measuring the potential of the solution with a tin electrode, and a SCE reference electrode (0.241 V).


The mixture was made by combining 20.00 mL of 30.12 mM Sn(NO3)2 and 50.00 mL of the unknown sulfide solution. The Ksp for tin sulfide is 1.3×10–26.


The cell potential was measured to be –1.080 V. What is the concentration of S2– in the unknown solution?

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  1. (10 points) You are measuring the amount of iron via a colorimetric reaction with 1,10phenanthroline. You can quantify the amount of iron by the absorbance that you can measure form the metal-dye complex.


You have added an excess of the 1,10-phenanthroline to a solution containing an unknown amount of iron. When the absorbance is measured you obtain a value of

0.488 AU.


You then mix 15.00 mL of that unknown solution with 30.00 mL of an iron standard solution that contains 73.23 µM iron and an excess of the 1,10-phenanthroline. When you measure the absorbance of this solution you get an absorbance value of 0.682 AU.


What is the concentration of iron in the unknown solution?


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  1. (10 points) A liquid chromatographic (LC) instrument is being used to quantify the calcium content of a soy milk. To test the detector for the LC a standard solution containing 515 ppm Ca2+ and 145 ppm Cd2+ is measured, and the peak areas for the two metals are found to be 1531 and 583 respectively.


A 20.00 mL sample of the soy milk is mixed with 5.00 mL of the cadmium internal standard (225 ppm). When the peak areas are obtained for calcium and cadmium they are found to be 1450 and 181 respectively.


What is the ppm concentration of calcium in the soy milk?

Note: keep all concentrations in ppm throughout this problem for simplicity.

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E =K+ 0.05916 log([A]+KA,I [I]zzAI ) KA,I = [Az]zAI


word image 2620 [I]

SA Sspike


CA %VA (+Cspike %’Vspike (*

CA ‘ * &VT ) & VT )

SA Sspike


%VO ( C %V ( %V (

CA ‘ * A O *+Cspike spike *

&VF ) &VF )


= =


b± b2 −4ac



& VF )

word image 908 word image 909


K = ×


Selected Standard Reduction Potentials


E° (Volts)

Mg(OH)+ + H+ + 2e– ⇌ Mg(s) + H2O


Mg(OH)2(s) + 2e– ⇌ Mg(s) + 2OH–


IrCl62– + e ⇌ IrCl63–


IrCl62– + 4e ⇌ Ir(s) + 6Cl


Sn4+ + 2e ⇌ Sn2+


Sn2+ + 2e ⇌ Sn(s)


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