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# Ag cations are attracted to the solid ag electrode

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Ag + cations are attracted to the solid Ag electrode where they are reduced to Ag(s). 011 3.3points A GALVANIC cell converts 1. chemical potential energy into electrical potential energy. correct 2. chemical potential energy into chemical potential energy. 3. electrical potential energy into chemical potential energy. 4. electrical potential energy into electrical potential energy. Explanation: Definition 012 3.3points A student was given a standard Fe(s) | Fe 2+ (aq) half-cell and another half- cell containing an unknown metal M im- mersed in 1 M MNO 3 (aq). When these two half-cells were connected at 25 C, the com- plete cell functioned as a galvanic cell with E = 1 . 24 V. The reaction was allowed to con- tinue overnight and the two electrodes were weighted. The iron electrode was found to be lighter and the unknown metal electrode was heavier. What is the standard potential of the unknown M + / M couple? 1. +2 . 04 V 2. +0 . 8 V correct 3. - 0 . 8 V 4. +1 . 68 V 5. - 0 . 36 V Explanation: E cell = 1 . 24 V The unknown metal ions are reduced, in- creasing the weight of the unknown metal electrode. The cell can be written as Fe(s) | Fe 2+ (aq) || M + (aq) | M(s) showing that the M + / M electrode is the cath- ode, because this is where reduction occurs. At the anode, Fe(s) Fe 2+ + 2 e - E = +0 . 44 V E cell = E cathode - E anode E cathode = 1 . 24 V + E anode = 1 . 24 V + ( - 0 . 44 V) = 0 . 8 V . 013 3.3points Consider the half-reactions and the balanced equation for the cell reaction represented by the skeletal equation Fe 3+ (aq) + H 2 (g) Fe 2+ (aq) + H + (aq) . What is the proper cell diagram for this reaction? 1. Pt(s) | H 2 (g) | H + (aq) || Fe 2+ (aq) | Fe 3+ (aq) 2. Pt(s) | Fe 3+ (aq) , Fe 2+ (aq) || H + (aq) | H 2 (g) | Pt(s)

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casey (rmc2555) – Homework 11 – holcombe – (51395) 5 3. Fe(s) | Fe 3+ (aq) , Fe 2+ (aq) || H + (aq) | H 2 (g) | Pt(s) 4. Pt(s) | H 2 (g) | H + (aq) || Fe 3+ (aq) , Fe 2+ (aq) | Pt(s) correct Explanation: The two half-reactions, written as reduc- tions, are Fe 3+ (aq) + e Fe 2+ (aq) 2 H + (aq) + 2 e H 2 (g) Equate e : 2 bracketleftbig Fe 3+ (aq) + e Fe 2+ (aq) bracketrightbig H 2 (g) 2 H + (aq) + 2 e Add the balanced half reactions: 2 Fe 3+ (aq) + H 2 (g) 2 Fe 2+ (aq) + 2 H + (aq) The cell diagram is Pt(s) | H 2 (g) | H + (aq) || Fe 3+ (aq) , Fe 2+ (aq) | Pt(s) 014 3.3points Zinc (Anode) Silver (Cathode) 1 . 56 V V Voltmeter e e 1 M Zn 2+ (aq) 1 M Ag + (aq) Salt bridge to carry ions In this electrochemical cell, what is the ox- idation half reaction? 1. Ag(s) Ag + (g) + e 2. Ag + (g) + e Ag(s) 3. Zn(s) Zn 2+ (aq) + 2 e correct 4. Zn 2+ (aq) + 2 e Zn(s) Explanation: Zn(s) + 2 Ag + (aq) Zn 2+ (aq) + 2 Ag(s) Oxidation occurs at the anode. In this cell the oxidation half reaction is Zn(s) Zn 2+ (aq) + 2 e . 015 3.3points What is the cathode in Ag(s) | Ag + (aq) || Fe 2+ (aq) | Fe(s) Ag + + e Ag E red = +0 . 80 Fe 2+ + 2 e Fe E red = - 0 . 44 and what type cell is it? 1. Not enough information is provided. 2. Ag(s) | Ag + (aq); a battery 3. Fe 2+ (aq) | Fe(s); a battery 4. Ag(s) | Ag + (aq); an electrolytic cell 5. Fe 2+ (aq) | Fe(s); an electrolytic cell cor- rect Explanation: The diagram A | B || C | D is read as follows: A B + ne (oxidation) C + me D (reduction) Since reduction occurs at the cathode, the cathode is Fe 2+ (aq) | Fe(s).
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• Fall '07
• Holcombe

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