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01:160:162 Lecture Notes - Lecture 22: Bayerischer Rundfunk, Cathodic Protection, Sodium Sulfate

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rubysalmon273
2 Nov 2016
School
Rutgers University
Department
Chemistry
Course
01:160:162
Professor
Tavss

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Document Summary

Based on the e: chart, which metal, iron or. Aluminum is a more active metal (more easily oxidized). Aluminum is very reactive and actually does oxidize. Then why is corrosion of iron so common (costs billions of dollars every year) but we. Corrosion is a process which oxidizes the iron to its. Al3++ 3e- al aluminum should corrode more easily? never see corrosion of aluminum? protective oxide coating which adheres to the aluminum and protects it from further oxidation. ions, either fe2+or fe3+. A shiny dry nail exposed to gaseous o2 will stay shiny and uncorroded indefinitely. The oxidizing agent is o2, either oxygen gas dissolved in water or oxygen gas in the air in contact with water. two separate areas (cathode and anode) where the reaction occurs. with its familiar red color. Since corrosion is a oxidation-reduction process, there are two half reactions, and actually. Fe(oh)2 can get further oxidized to fe(oh)3, which can get dehydrated to fe2o3,

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Related Questions

Corrosion and redox reactions chem questions - HELP APPRECIATED

QUESTION ONE - In the following chemical reaction, CaO is the reducing agent.

2Ca(s) + O2 (g) → 2CaO (s)

True
False

QUESTION TWO - What is the oxidation state of Nitrogen in K3Fe(CN)6 ?

QUESTION THREE - Identify the correct statement(s) with regards Zinc in Contact with Magnesium experiment

A.

Magnesium metal could be used as a suitable coating for both galvanized and non-galvanized nails to protect both iron and zinc from corrosion.
B.

As the reaction proceeds, Copper metal is deposited on the exposed surface of the nail.
C.

Magnesium is oxidized from Mg(s) to Mg2+ when in contact with the Cu(NO3)2 solution
D.

Aluminum metal cannot be used instead of magnesium to prevent corrosion of zinc under the same conditions.

E. Magnesium forms a physical barrier prevent the Cu(NO3)2 solution from coming into contact with the zinc-plated galvanized nail.

QUESTION FOUR - Which of the following chemical equations correspond to redox reactions? Select all that apply.

A.

NH3 (aq) + HCl (aq) → NH4Cl (aq)
B.

2AgOOCCH3 (aq) + Zn(s) → Zn(OOCCH3)2 (aq) + 2Ag(s)
C.

Au(s) + BrF3 (aq) + KF (aq) → Br2 (l) + KAuF4 (aq)
D.

Na2CO3 (aq) + H2SO4(aq) → 2Na+ (aq) + SO42- (aq) + CO2 (g) + H2O (l)
E.

KNO3 (aq) + NaOH (aq) → KOH (aq) + NaNO3 (aq)

QUESTION FIVE -

Identify the correct statement(s) with regards to the last part of Experiment 6: Zinc in Contact with Magnesium

A.

The addition of sodium chloride is necessary for Cu(NO3)2 solution to corrode the zinc-plated galvanized nail
B.

As the reaction proceeds, more zinc metal is deposited on the exposed surface of the nail.
C.

Magnesium forms a physical barrier prevent the Cu(NO3)2 solution from coming into contact with the zinc-plated galvanized nail.
D.

Magnesium is oxidized from Mg(s) to Mg2+ when in contact with the Cu(NO3)2 solution

Magnesium metal is able to shuttle electrons easily to the zinc, thereby reducing the amount of zinc undergoing corrosion from the Cu(NO3)2 solution

QUESTION SIX - Make three matches with the following metals and a substance that may act as a suitable sacrificial electrode. All three metals have unique choices, you CANNOT reuse choices (for Example: if you pair Nickel metal with A- you cannot use A again for another metal)

Nickel metal

Iron metal

Silver metal
A.

Iron- sacrificial electrode
B.

Manganese- sacrificial electrode
C.

Gold-sacrificial electrode
D.

Copper - sacrificial electrode
E.

PbSO4 - sacrificial electrode

A. A voltaic cell is constructed based on the reaction of Ag(CN)2-(aq) with Cr(s) producing Ag(s) and Cr3+(s). Identify the correct cell diagram.

a.

Ag(CN)2-(aq) | Cr(s) || Ag(s) | Cr3+(aq)

d.

Ag(CN)2-(aq) | Ag(s) || Cr(s) | Cr3+(aq)

b.

Ag(s) | Cr3+(aq) || Ag(CN)2-(aq) | Cr(s)

e.

Cr(s) | Cr3+(aq) || Ag(CN)2-(aq) | Ag(s)

c.

Cr(s) | Cr3+(aq) || Ag(s) | Ag(CN)2-(aq)

B. Use the table of standard reduction potentials below to identify the metal or metal ion that is the strongest oxidizing agent.

Half-reaction

Pb4+ + 2 e- ® Pb2+

+1.80

Au3+ + 3 e- ® Au

+1.50

Fe3+ + 3 e- ® Fe

+0.771

I2 + 2 e- ® 2 I-

+0.535

Pb2+ + 2 e- ® Pb

-0.124

Al3+ + 3 e- ® Al

-1.66

Mg2+ + 2 e- ® Mg

-2.37

K+ + e- ® K

-2.93

a.

Pb4+

d.

K

b.

Pb2+

e.

Al

c.

K+

C. Silver tarnish (Ag2S) can be removed by immersing silverware in a hot solution of baking soda (NaHCO3) in a pan lined with aluminum foil; however, foul-smelling hydrogen sulfide gas (H2S) is produced. Which of the following statements is correct?

Silver/silver(I)

+0.799

Sulfur/hydrogen sulfide

+0.141

Aluminum/aluminum(III)

-1.662

Sodium/sodium(I)

-2.713

a.

Aluminum ions react with S2-, form aluminum sulfide, and gaseous carbon dioxide is released.

b.

Silver ions in the presence of the baking soda (NaHCO3) oxidize sulfide to elemental sulfur that attacks the aluminum foil, which produces aluminum sulfide.

c.

The aluminum acts as a reducing agent for the silver(I) in silver sulfide; then bicarbonate ion protonates the sulfide ion that is released.

d.

Aluminum is plated onto the silver surface, making it shiny again, and then the reaction of bicarbonate with aluminum oxide releases CO2.

e.

Silver in Ag2S reduces the aluminum, becomes metallic silver in the process, and releases hydrogen sulfide, H2S.

D. Using the following data, determine the standard cell potential for the electrochemical cell constructed using the following reaction: Zn(s) + Pb2+(aq) ® Zn2+(aq) + Pb(s).

Half-reaction Standard reduction potential

Zn2+(aq) + 2 e- ® Zn(s) -0.763

Pb2+(aq) + 2 e- ® Pb(s) -0.126

a.

+0.637 V

d.

-0.889 V

b.

-0.637 V

e.

+0.889 V

c.

+1.274 V

E. Based on the information in the table of standard reduction potentials below, what is the standard cell potential for an electrochemical cell that has iron (Fe) and magnesium (Mg) electrodes immersed in 1M Fe3+ and Mg2+ solutions? Also, identify the cathode.

Half-reaction

Pb4+ + 2 e- ® Pb2+

+1.80

Au3+ + 3 e- ® Au

+1.50

Fe3+ + 3 e- ® Fe

+0.771

I2 + 2 e- ® 2 I-

+0.535

Pb2+ + 2 e- ® Pb

-0.124

Al3+ + 3 e- ® Al

-1.66

Mg2+ + 2 e- ® Mg

-2.37

K+ + e- ® K

-2.93

a.

+1.60 V with Fe as the cathode

d.

-3.14 V with Mg as the cathode

b.

+3.14 V with Mg as the cathode

e.

+3.14 V with Fe as the cathode

c.

-3.14 V with Fe as the cathode