Resolução de Química: ENEM 2025 - Prova Amarela - Questão 126 | Gabarito Extraoficial Comentado

Question 126 - Silver objects tarnish when in contact with sulfur-containing compounds due to the formation of a thin layer of silver sulfide. A simple method to brighten the object consists of lining a container with aluminum foil, adding an aqueous solution of sodium chloride to the container, and then immersing the tarnished silver object. In about three minutes, the silver returns to its original color. The semi-empirical equations and their respective standard reduction potentials are useful for understanding the phenomena that occur. Ag₂S (s) + 1 e⁻ → 2 Ag (s) + S²⁻ (aq) –0.69 V O₂ (g) + 4 H⁺ (aq) + 4 e⁻ → 2 H₂O (l) +1.23 V Al³⁺ (aq) + 3 e⁻ → Al (s) –1.68 V (SARTORI, R.; BATISTA, E. F.; FANTINEL-FILHO, D. The tarnishing and cleaning of silver objects: a simple and easy-to-perform experiment involving oxidation-reduction reactions. Química Nova na Escola, n. 30, 2008 (adapted)). The values ​​of the standard potential differences of the reactions representing the darkening and lightening of the silver object are, respectively: A) +0.54 V and +2.37 V. B) +1.22 V and +0.90 V. C) –0.51 V and +5.43 V. D) –1.52 V and +4.89 V. E) +0.15 V and –1.29 V. Supporting videos: Playlist with all the Chemistry questions from the 2025 ENEM exam:    • Resolução ENEM 2025 - Química (Prova Amarela)   If the video helps you, leave a like — this strengthens my work and encourages me to continue bringing complete solutions, corrections, and detailed explanations of the exams. #ENEM2025 #ENEMChemistry #UnofficialAnswerKey #ENEMResolution #ExplainedChemistry #ENEM2025Questions #ENEM2025AnswerKey #StepByStepResolution #ChemistryForENEM #ENEM2025Exam #ENEMCorrection #ChemistryFromZero #BasicChemistry #OrganicChemistry #GeneralChemistry #ProfessorFelippeGarcia #ProfessorFelippeG #ChemicalReasoning #CommentedResolution #QuestionByQuestion