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Silver tarnish is the result of the oxide on the silver surface racting with hydrogen sulfide (H2S) in air. This leaves a black film of silver sulfide (Ag2S). Polishing the tarnished silver will restore the shine but at the expense of some of the silver metal. An alternative process is to allow aluminum to reduce the silver in the presence of a solution of sodium bicarbonate (baking sodium) electrolyte.

2. Assume that Aluminum and Silver Sulfide are the starting substances (reactants) in the reaction:

(A) Write a balanced chemical equation describing the "re-creation" of silver, using the information in the case study.

(B) State the names of the products that are produced from this reaction.

(C) What type reaction(s) is/are being represented by the chemical reaction you wrote in part (a)?

(D) Is the reaction in part(a) an oxidation-reduction (redox) reaction?

(E) If this is a redox reaction, the identify the following:

  • What is undergoing oxidation (what is being oxidized)? Support your answer using oxidation number.
  • What is undergoing reduction (what is being reduced)? Support your answer using oxidation numbers.
  • What is the reducing agent?
  • What is the oxidizing agent?

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Althea Arnoco
Althea ArnocoLv5
7 Nov 2020

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Related questions

The tarnish of silver objects is a coating of silver sulfide (Ag2S), which can be removed by putting the silver in contact with aluminum metal in a dilute solution of baking soda or salt. The equation for the cleaning reaction is

 

The sulfur in these compounds has a -2 oxidation number. What are the oxidizing and reducing agents in the cleaning reaction?

 

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


Initial observations: before beginning Observations Observations after 30 minutes Chemical equation Element that is oxidized Element that is reduced Spectator ion Oxidizing agent Reducing agent www.HOLscience.com 16 ©Hands-On Labs, Inc. Experiment Oxidation-Reduction Activity Series Questions A. Define oxidation, reduction, and oxidation number. Describe how oxidation and reduction affect the oxidation number of an element. B. Define oxidizing agent, reducing agent, and spectator ion. C. In the reaction of copper and silver nitrate, a new substance appeared in the test tube. Describe the physical appearance of the substance and identify its chemical formula. D. Given an activity series in which the most active metals are at the top of the list and the least active metals are at the bottom of the list, would copper be listed above silver or would silver be listed above copper? Support your answer with data from Data Table 1. E. Solid copper sulfide and silver nitrate react to form copper (II) nitrate and solid silver sulfide. Write a balanced chemical equation that describes the reaction. Identify the oxidation number of each element in the reaction. (You do not need to include the total contribution of charge.) Is this reaction a redox reaction or a non-redox reaction? Explain your answer. www.HOLscience.com 17 ©Hands-On Labs, Inc. Experiment Oxidation-Reduction Activity Series Exercise 2: Creating an Activity Series Data Table 2. Redox Reactions of Copper, Lead, and Zinc Solid metal Well ID Solution Immediate observations 30 Minute Observations Cu A1 Pb(NO3 ) 2 A2 Zn(NO3 ) 2 Pb B1 CuSO4 B2 Zn(NO3 ) 2 Zn C1 CuSO4 C2 Pb(NO3 ) 2 Data Table 3. Potential Redox Reactions and Chemical Equations Metal and Metallic Solution Reaction Occurred? Chemical Equation Cu + Pb(NO3 ) 2 Cu + Zn(NO3 ) 2 Pb + CuSO4 Pb + Zn(NO3 ) 2 Zn + CuSO4 www.HOLscience.com 18 ©Hands-On Labs, Inc. Experiment Oxidation-Reduction Activity Series Zn + Pb(NO3 ) 2 Questions A. List each of the metals tested in Exercise 2. Indicate the oxidation number when each element is pure and the oxidation number when each element is in a compound. B. Which of the metals in Exercise 2 was the strongest oxidizing agent? Was there an instance when this metal also acted as a reducing agent? Explain your answer using data from Data Table 3. C. Which of the metals in Exercise 2 was the strongest reducing agent? Was there an instance when this metal also acted as an oxidizing agent? Explain your answer using data from Data Table 3. D. How does ease of oxidation correlate with activity? Do highly active metals tend to donate electrons or accept electrons from other metals? E. Create an activity series for copper, lead, and zinc. Place the most active metal at the top of the list.

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