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Electrochemical cells, Bonds, and Lattice

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Question 1 Consider the following electrochemical cell:
Cu(s) | CuSO4(aq) || KCl(aq) | Cl2(g) | C(graphite).
Identify the matching pairs below. (transferred from anode to cathode, produced at the cathode, oxidizing agent, does not lose nor gain mass, reducing agent, loses mass)

Cu metal
Cl2(g)
electrons
Cu2+ ions
chloride ions
C(graphite) electrode
Cu electrode

Question 2 (0.7 points)
What is the E°cell for the cell that forms from the following half reactions?
Fe3+(aq) + e- ---> Fe2+(aq)
Zn2+(aq) + 2e- ---> Zn(s)

a. -1.53 V

b. -0.01 V

c. ) 0.78 V

d. 0.01 V

e. 1.53 V

Question 3 (0.7 points)
Which one of the following statements is true?

a. Only lead storage batteries can be placed in series.

b. A lead storage battery's voltage output depends strongly on the temperature.

c. Metallic lead is reduced at the cathode of a lead storage battery.

d. A dry cell battery is not rechargeable.

e. A fuel cell does not require a continuous supply of reactants.

Question 4 (0.9 points)
Calculate the cell potential for the reaction
Zn(s) + 2 Cr+3(aq)[0.010 M] ---> 3 Zn+2(aq)[0.020 M] + 2 Cr(s)
given, Cr+3(aq) + 3e- ---> Cr(s) . . . . . . . Eo = -0.74 V
Zn+2(aq) + 2e- ---> Zn(s) . . . . . . .Eo = -0.76 V

a. +0.01 V

b. -0.01 V

c. + 0.03 V

d. -0.03 V

e. -0.02 V

Question 5 (1 point)
The following cell was observed to have an emf of 2.29 volts at 25.0oC :
Zn(s) | Zn2+(aq,0.112 M) || Cl-(aq) | Cl2(g; 0.472 atm) | Pt(s) .
Use tables of standard reduction potentials in Silberberg to calculate the concentration of chloride ion in the cathode compartment, [Cl-] / M . Your answer should be dimensionless (no units) and be given to 2 significant figures.
Scientific notation should be entered as 6.2e-3 for 6.2 x 10-3.
Answer

Question 6 (0.9 points)
Which of the following statements are FALSE?

a. &#61508;Go < 0 for
Br2(l) + 2 Hg(l) ---> 2 Br-(aq) + Hg22+(aq).

b. &#61508;Go < 0 for
NO3-(aq) + 4 H+(aq) + Au(s) ---> NO(g) + 2 H2O(l) + Au3+(aq).

c. The cell potential for
Co|Co2+(0.1 M)||Fe3+(0.5 M)|Fe2+(1.5 M)|Pt
is greater than 1.05 V.

d. The cell potential for
Co|Co2+(0.25 M)||Fe3+(0.5 M)|Fe2+(1.0 M)|Pt
is greater than 1.05 V.

e. The cell potential for
Cu|Cu2+(2.0 M)||Cl2(2.0 atm)|Cl-(2.0 M)|Pt
is less than 1.02 V.

Question 8 (0.9 points)
A certain metal crystallizes in a structure that has 4 atoms per unit cell, and the unit cell is a cube. How is the lattice described for this metal?

a. ) body centered cubic

b. ) simple cubic

c. ) face centered cubic

d. ) hexagonal

e. ) tetragonal

Question 9 (0.7 points)
Which has the highest melting point?

a. ) Na

b. ) Mg

c. ) W

d. ) Ba

e. ) they all exhibit the same melting point

Question 10 (0.8 points)
Which of the species listed below can form hydrogen bonds with water molecules?

a. Na+ ions

b. CH3OH (methanol)

c. C2H6 (ethane)

d. HCOOH (formic acid)

e. CCl4 (carbon tetrachloride)

Question 11 (0.8 points)
Which of the following has the smallest bond angles?

a. ) CO2

b. ) SO2

c. ) SO3

d. ) SO42-

Question 12 (0.8 points)
Select the false statements from the following:

a. XeF4 is tetrahedral.

b. CH2F2 is nonpolar.

c. The four bond moments of SiH4 add to zero.

d. The nitrite ion, NO2-, is linear.

e. The nitrate ion, NO3-, is AB3E.

Bonus questions:
1. Chlorine gas can oxidize zinc metal
a. Write half-reactions involved
b. Write the cell diagram for this process
c. Mark anode and cathode. Which reaction occurs at anode? Which at cathode?
2. In an experiment, chlorine is formed in reaction of potassium permanganate with concentrated hydrochloric acid. Write equation for the reaction; balance it showing all steps of balancing.

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https://brainmass.com/chemistry/electrochemical-potentials/electrochemical-cells-bonds-lattice-11055

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Answers questions form Electrochemical cells, half reactions, lead storage batteries, lattice, melting point, hydrogen bonds, bond angles etc.

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Quantitative Analysis and Electrochemistry

IX) Given the following information, which of the statements is true?
Cu2+(aq) + e- &#8594; Cu+(aq) Eº = 0.34V
2 H+(aq) + 2 e- &#8594; H2(g) Eº = 0.0V
Fe2+(aq) + 2 e- &#8594; Fe(s) Eº = - 0.44V
Ni(s) &#8594; Ni2+(aq) + 2 e- Eº = 0.25V

a) Cu+2(aq) is the strongest oxidizing agent

b) Cu+2(aq) is the weakest oxidizing agent

c) Ni(s) is the strongest oxidizing agent

d) Fe(s) would be the weakest reducing agent

e) H+(aq) would be the strongest oxidizing agent

X) A galvanic electrochemical cell has the overall reaction:
Mg(s) + Pb2+(aq) &#8594; Mg2+(aq) + Pb(s)
Which of the following statements is FALSE?

a) The mass of the Mg electrode will decrease.

b) Negative ions from the salt bridge will flow to the chamber with the Mg electrode.

c) Electrons in the external circuit will flow from the Pb electrode to the Mg electrode.

d) The concentration of Mg2+ will increase.

e) The cell reaction will be spontaneous.
GMU, CHEM 321 Final Initial _____________ Page 3 of 9
XI) The portion of a pH electrode that develops a potential when exposed to hydrogen ions is

a) a glass membrane with cavities designed to hold H+ that are moving through a concentration gradient .

b) a drop of liquid mercury that undergoes a redox reaction with a mercury salt .

c) a silver wire that is oxidized to Ag+ in the presence of H+.

d) a plastic polymer membrane that allows diffusion of H+ across the membrane.

e) a crystal of a Li+ salt that reduces to Li when exposed to H+.

XII) The path that excitation radiation travels in a single-beam UV-visible spectrophotometer is

a) source &#8594; sample &#8594; wavelength selector &#8594; detector

b) source &#8594; wavelength selector &#8594; sample &#8594; detector

c) source &#8594; wavelength selector &#8594; detector

d) source &#8594; sample &#8594; detector &#8594; wavelength selector

e) source &#8594; wavelength selector &#8594; sample &#8594; wavelength selector &#8594; detector

XIII) The most common mechanism of separation used in chromatography is:

a) ion exchange

b) affinity

c) partition

d) molecular exclusion

XIV) Surface adsorption is a form of coprecipitation phenomena in which

a) an impurity sticks to the precipitate surface by electrostatic attraction.

b) one type of ion in the crystal lattice of the precipitate is replaced by another type of ion that has a similar size.

c) the precipitate is heated and trapped as a gas.

d) an impurity is trapped inside of the growing precipitate crystals.

e) an impurity precipitates on top of a previously formed precipitate.

XV) Qualitative analysis is best defined as

a) identification of an analyte in a sample.

b) determination of the mass of a sample.

c) determination of the analyte concentration in a sample.

d) taking a representative sample from a bulk quantity.

e) separation of analytes in a sample.

IX) Given the following information, which of the statements is true?
Cu2+(aq) + e- &#8594; Cu+(aq) Eº = 0.34V
2 H+(aq) + 2 e- &#8594; H2(g) Eº = 0.0V
Fe2+(aq) + 2 e- &#8594; Fe(s) Eº = - 0.44V
Ni(s) &#8594; Ni2+(aq) + 2 e- Eº = 0.25V

a) Cu+2(aq) is the strongest oxidizing agent

b) Cu+2(aq) is the weakest oxidizing agent

c) Ni(s) is the strongest oxidizing agent

d) Fe(s) would be the weakest reducing agent

e) H+(aq) would be the strongest oxidizing agent

X) A galvanic electrochemical cell has the overall reaction:
Mg(s) + Pb2+(aq) &#8594; Mg2+(aq) + Pb(s)
Which of the following statements is FALSE?

a) The mass of the Mg electrode will decrease.

b) Negative ions from the salt bridge will flow to the chamber with the Mg electrode.

c) Electrons in the external circuit will flow from the Pb electrode to the Mg electrode.

d) The concentration of Mg2+ will increase.

e) The cell reaction will be spontaneous.
GMU, CHEM 321 Final Initial _____________ Page 3 of 9
XI) The portion of a pH electrode that develops a potential when exposed to hydrogen ions is

a) a glass membrane with cavities designed to hold H+ that are moving through a concentration gradient .

b) a drop of liquid mercury that undergoes a redox reaction with a mercury salt .

c) a silver wire that is oxidized to Ag+ in the presence of H+.

d) a plastic polymer membrane that allows diffusion of H+ across the membrane.

e) a crystal of a Li+ salt that reduces to Li when exposed to H+.

XII) The path that excitation radiation travels in a single-beam UV-visible spectrophotometer is

a) source &#8594; sample &#8594; wavelength selector &#8594; detector

b) source &#8594; wavelength selector &#8594; sample &#8594; detector

c) source &#8594; wavelength selector &#8594; detector

d) source &#8594; sample &#8594; detector &#8594; wavelength selector

e) source &#8594; wavelength selector &#8594; sample &#8594; wavelength selector &#8594; detector

XIII) The most common mechanism of separation used in chromatography is:

a) ion exchange

b) affinity

c) partition

d) molecular exclusion

XIV) Surface adsorption is a form of coprecipitation phenomena in which

a) an impurity sticks to the precipitate surface by electrostatic attraction.

b) one type of ion in the crystal lattice of the precipitate is replaced by another type of ion that has a similar size.

c) the precipitate is heated and trapped as a gas.

d) an impurity is trapped inside of the growing precipitate crystals.

e) an impurity precipitates on top of a previously formed precipitate.

XV) Qualitative analysis is best defined as

a) identification of an analyte in a sample.

b) determination of the mass of a sample.

c) determination of the analyte concentration in a sample.

d) taking a representative sample from a bulk quantity.

e) separation of analytes in a sample.

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