This is a true story; can you explain what happened? Prior to a really important dinner party, the hostess discovered that her silverware was very tarnished. She needed a quick fix. She remembered reading that the tarnish (Ag₂S) would be removed if you immersed the silverware in a hot solution of baking soda (NaHCO₃) in a pan lined with aluminum foil. So she did, and so it was, but she noticed a bit of a rotten egg smell (H₂S) being produced. Metal/Metal ion silver/silver(I)
0) 799
Aluminum/aluminum(III) -1.677

Question

This is a true story; can you explain what happened? Prior to a really important dinner party, the hostess discovered that her silverware was very tarnished. She needed a quick fix. She remembered reading that the tarnish (Ag₂S) would be removed if you immersed the silverware in a hot solution of baking soda (NaHCO₃) in a pan lined with aluminum foil. So she did, and so it was, but she noticed a bit of a rotten egg smell (H₂S) being produced. Metal/Metal ion

silver/silver(I)
0) 799
Aluminum/aluminum(III) -1.677

Quizplus · Accepted Answer

Aluminum is a strong reducing agent and can reduce silver ions to metallic silver, which explains why the tarnish was removed and the silverware was shiny again. The bicarbonate ion, NaHCO3, can protonate sulfide ions released from the silver sulfide, Ag2S, to form hydrogen sulfide gas, which explains the rotten egg smell. The reaction between aluminum ions and sulfide ions resulting in the formation of aluminum sulfide precipitate and carbon dioxide gas, as described in choice A, does not occur in this case. The oxidation of sulfide to elemental sulfur that attacks aluminum foil, as described in choice B, is not supported by the reaction conditions. Similarly, the plating of aluminum on the silver surface, as described in choice D, does not occur under these conditions. Choice E implies the formation of hydrogen sulfide gas, but the source of the hydrogen atom in H₂S is not explained.

This Is a True Story; Can You Explain What Happened