Using standard potentials from Table 17.1, decide whether at standard concentrations ⓐ the reaction 2Fe3+(aq) + 2I-(aq) → 2Fe2+(aq) + I2(s) will occur. ⓑ Fe(s) will be oxidized to Fe2+ by treatment with hydrochloric acid. ⓒ a redox reaction will occur when the following species are mixed in acidic solution: Cl-, Fe2+, Cr2+, I2.

Question

Using standard potentials from Table 17.1, decide whether at standard concentrations

Table 17.1 Standard Potentials in Water Solution at 25°C

Lithium is the strongest reducing agent. O = strongest oxidizing agent; R = strongest reducing agent. Fluorine is the strongest oxidizing agent. Lithium and fluorine are very dangerous materials to work with.	AcidicSolution,[latex][H^{+}][/latex] = 1 M
	[latex]E°_{red}[/latex](V)
	-3.040 -2.936 -2.906 -2.869 -2.714 -2.357 -1.680 -1.182 -0.762 -0.744 -0.409 -0.408 -0.402 -0.356 -0.336 -0.282 -0.236 -0.152 -0.141 -0.127 0.000 0.073 0.144 0.154 0.155 0.161 0.339 0.518 0.534 0.769 0.796 0.799 0.908 0.964 1.001 1.077 1.229 1.229 1.330 1.360 1.458 1.498 1.512 1.687 1.763 1.953 2.889		→Li(s) → K(s) → Ba(s) → Ca(s) →Na(s) → Mg(s) → Al(s) → Mn(s) → Zn(s) → Cr(s) → Fe(s) → [latex]Cr^{2+}(aq)[/latex] → Cd(s) → Pb(s) + [latex]SO_{4}^{2-}(aq)[/latex] → Tl(s) → Co(s) →Ni(s) → Ag(s) + [latex]I^{-}(aq)[/latex] → Sn(s) → Pb(s) →[latex]H_{2}(g)[/latex] → Ag(s) + [latex]Br^{-}(aq)[/latex] →[latex]H_{2}S(aq)[/latex] → [latex]Sn^{2+}(aq)[/latex] → [latex]SO_{2}(g) + 2H_{2}O[/latex] → [latex]Cu^{+}(aq)[/latex] → Cu(s) → Cu(s) → [latex]2I^{-}(aq)[/latex] → [latex]Fe^{2+}(aq)[/latex] → 2Hg(l) → Ag(s) →[latex]Hg_{2}^{2+}(aq)[/latex] →NO(g) + [latex]2H_{2}O[/latex] → [latex]Au(s) + 4Cl^{-}(aq)[/latex] → [latex]2Br^{-}(aq)[/latex] → [latex]2H_{2}O[/latex] → [latex]Mn^{2+}(aq) + 2H_{2}O[/latex] → [latex]2Cr^{3+}(aq) + 7H_{2}O[/latex] → [latex]2Cl^{-}(aq)[/latex] →[latex]\frac{1}{2} Cl_{2}(g) + 3H_{2}O[/latex] → Au(s) → [latex]Mn^{2+}(aq) + 4H_{2}O[/latex] → [latex]PbSO_{4}(s) + 2H_{2}O[/latex] → [latex]2H_{2}O[/latex] → [latex]Co^{2+}(aq)[/latex] → 2[latex]F^{-}(aq)[/latex]	[latex]Li^{+}(aq) + e^{-}[/latex] [latex]K^{+}(aq) + e^{-}[/latex] [latex]Ba^{2+}(aq) + 2e^{-}[/latex] [latex]Ca^{2+}(aq) + 2e^{-}[/latex] [latex]Na^{+}(aq) + e^{-}[/latex] [latex]Mg^{2+}(aq) + 2e^{-}[/latex] [latex]Al^{3+}(aq) + 3e^{-}[/latex] [latex]Mn^{2+}(aq) + 2e^{-}[/latex] [latex]Zn^{2+}(aq) + 2e^{-}[/latex] [latex]Cr^{3+}(aq) + 3e^{-}[/latex] [latex]Fe^{2+}(aq) + 2e^{-}[/latex] [latex]Cr^{3+}(aq) + e^{-}[/latex] [latex]Cd^{2+}(aq) + 2e^{-}[/latex] [latex]PbSO_{4}(s) + 2e^{-}[/latex] [latex]Tl^{+}(aq) + e^{-}[/latex] [latex]Co^{2+}(aq) + 2e^{-}[/latex] [latex]Ni^{2+}(aq) + 2e^{-}[/latex] [latex]AgI(s) + e^{-}[/latex] [latex]Sn^{2+}(aq) + 2e^{-}[/latex] [latex]Pb^{2+}(aq) + 2e^{-}[/latex] [latex]2H^{+}(aq) + 2e^{-}[/latex] [latex]AgBr(s) + e^{-}[/latex] [latex]S(s) + 2H^{+}(aq) + 2e^{-}[/latex] [latex]Sn^{4+}(aq) + 2e^{-}[/latex] [latex]SO_{4}^{2-}(aq) + 4H^{+}(aq) + 2e^{-}[/latex] [latex]Cu^{2+}(aq) + e^{-}[/latex] [latex]Cu^{2+}(aq) + 2e^{-}[/latex] [latex]Cu^{+}(aq) + e^{-}[/latex] [latex]I_{2}(s) + 2e^{-}[/latex] [latex]Fe^{3+}(aq) + e^{-}[/latex] [latex]Hg_{2}^{2+}(aq) + 2e^{-}[/latex] [latex]Ag^{+}(aq) + e^{-}[/latex] [latex]2Hg^{2+}(aq) + 2e^{-}[/latex] [latex]NO_{3}^{-}(aq) + 4H^{+}(aq) + 3e^{-}[/latex] [latex]AuCl_{4}^{-}(aq) + 3e^{-}[/latex] [latex]Br_{2}(l) + 2e^{-}[/latex] [latex]O_{2}(g) + 4H^{+}(aq) + 4e^{-}[/latex] [latex]MnO_{2}(s) + 4H^{+}(aq) + 2e^{-}[/latex] [latex]Cr_{2}O_{7}^{2-}(aq) + 14H^{+}(aq) + 6e^{-}[/latex] [latex]Cl_{2}(g) + 2e^{-}[/latex] [latex]ClO_{3}^{-}(aq) + 6H^{+}(aq) + 5e^{-}[/latex] [latex]Au^{3+}(aq) + 3e^{-}[/latex] [latex]MnO_{4}^{-}(aq) + 8H^{+}(aq) + 5e^{-}[/latex] [latex]PbO_{2}(s) + SO_{4}^{2-}(aq) + 4H^{+}(aq) + 2e^{-}[/latex] [latex]H_{2}O_{2}(aq) + 2H^{+}(aq) + 2e^{-}[/latex] [latex]Co^{3+}(aq) + e^{-}[/latex] [latex]F_{2}(g) + 2e^{-}[/latex]
	Basic Solution, [latex][OH^{-}][/latex] = 1 M
	[latex]E°_{red}[/latex](V)
	-0.891 -0.828 -0.547 -0.445 -0.140 0.004 0.398 0.401 0.614 0.890	→ Fe(s) + 2 [latex]OH^{-}[/latex](aq) →[latex]H_{2}(g)[/latex] + 2 [latex]OH^{-}[/latex](aq) → [latex]Fe(OH)_{2}(s)[/latex] + [latex]OH^{-}[/latex](aq) → [latex]S^{2-}(aq)[/latex] →NO(g) + 4 [latex]OH^{-}[/latex](aq) →[latex]NO_{2}^{-}[/latex](aq) + 2 [latex]OH^{-}[/latex](aq) → [latex]ClO_{3}^{-}[/latex](aq) + 2 [latex]OH^{-}[/latex](aq) → 4 [latex]OH^{-}[/latex](aq) → [latex]Cl^{-}(aq)[/latex] + 6 [latex]OH^{-}[/latex](aq) → [latex]Cl^{-}(aq)[/latex] + 2 [latex]OH^{-}[/latex](aq)		[latex]Fe(OH)_{2}(s) + 2e^{-}[/latex] [latex]2H_{2}O + 2e^{-}[/latex] [latex]Fe(OH)_{3}(s) + e^{-}[/latex] [latex]S(s) + 2e^{-}[/latex] [latex]NO_{3}^{-}(aq) + 2H_{2}O + 3e^{-}[/latex] [latex]NO_{3}^{-}(aq) + H_{2}O + 2e^{-}[/latex] [latex]ClO_{4}^{-}(aq) + H_{2}O + 2e^{-}[/latex] [latex]O_{2}(g) + 2H_{2}O + 4e^{-}[/latex] [latex]ClO_{3}^{-}(aq) + 3H_{2}O + 6e^{-}[/latex] [latex]ClO^{-}(aq) + H_{2}O + 2e^{-}[/latex]

ⓐ the reaction

[latex]2Fe^{3+}(aq) + 2I^{-}(aq) → 2Fe^{2+}(aq) + I_{2}(s)[/latex]

will occur.

ⓑ Fe(s) will be oxidized to [latex]Fe^{2+}[/latex] by treatment with hydrochloric acid.

ⓐ

ANALYSIS
equation for the reaction [latex]2Fe^{3+}(aq) + 2I^{-}(aq) → 2Fe^{2+}(aq) + I_{2}(s)[/latex]	Information given:
Table 17.1 (standard reduction potentials)	Information implied:
Will the reaction occur?	Asked for:

STRATEGY

1. Assign oxidation numbers.
2. Write oxidation and reduction half-reactions. Include [latex]E°_{ox}[/latex] and [latex]E°_{red}[/latex].
3. Find E°. The reaction will occur if E° > 0.

ⓑ

ANALYSIS
oxidation half-reaction (Fe(s) → [latex]Fe^{2+}(aq) + 2e^{-}[/latex])	Information given:
Table 17.1 (standard reduction potentials)	Information implied:
Will HCl oxidize Fe?	Asked for:

STRATEGY

1. HCl(aq) is made up of two ions, [latex]H^{+}[/latex] and [latex]Cl^{-}[/latex]. Since an oxidizing agent is needed (to oxidize Fe to [latex]Fe^{2+}[/latex]), find either [latex]H^{+}[/latex] or [latex]Cl^{-}[/latex] (or both) in the left column of Table 17.1.
2. Write the possible half-reactions.
3. Write the redox reaction and find E°.

ⓒ

ANALYSIS
ions in acidic solution ([latex]Cl^{-}, Fe^{2+}, Cr^{2+}, I_{2}[/latex])	Information given:
Table 17.1	Information implied:
Will a redox reaction occur when the ions are mixed?	Asked for:

STRATEGY

1. Check the left column of Table 17.1 to determine which of the ions are oxidizing agents (i.e., they are reduced). Write the reduction half-reactions of the oxidizing agents.
2. Check the right column of Table 17.1 to determine which of the ions are reducing agents (i.e., they are oxidized). Write the reduction half-reactions of the reducing agents.
3. Write all possible combinations of oxidation and reduction half-reactions. The combination(s) that give positive E° values are possible.
4. Write the redox equation(s) for the reaction(s) that occur.

Accepted Answer

ⓐ

Fe: + 3 → +2 reduction

I: -1 → 0 oxidation

1. oxidation numbers

[latex]2Fe^{3+}(aq) + 2e^{-} → 2Fe^{2+}(aq)[/latex] [latex]E°_{red}[/latex] = +0.769 V
[latex]2I^{-}(aq) → I_{2}(s) + 2e^{-}[/latex] [latex]E°_{ox}[/latex] = -0.534 V

2. half-reactions

E° = 0.769 V + (-0.534 V) = +0.235 V
E° > 0, the reaction will occur at standard conditions.

E°

ⓑ

Only [latex]H^{+}[/latex] appears in the left column.	1. Oxidizing agent
[latex]2H^{+}(aq) + 2e^{-} → H_{2}(g)[/latex] [latex]E°_{red}[/latex] = 0.000 V [latex]Fe(s) → Fe^{2+}(aq) + 2e^{-}[/latex] [latex]E°_{ox}[/latex] = 0.409 V	2. Half-reactions
Fe(s) + [latex]2H^{+}(aq) → Fe^{2+}(aq) + H_{2}(g)[/latex] E° = 0.409 V E° > 0, HCl will oxidize Fe at standard conditions (Figure 17.6, page 536).	3. Redox reaction

ⓒ

[latex]Fe^{2+}(aq) + 2e^{-}[/latex] → Fe(s) [latex]E°_{red}[/latex] = -0.409 V [latex]I_{2}(s) + 2e^{-}[/latex] →[latex]2I^{-}(aq)[/latex] [latex]E°_{red}[/latex] = +0.534 V	1. Oxidizing agents
[latex]2Cl^{-}(aq) → Cl_{2}(g) + 2e^{-}[/latex] [latex]E°_{ox}[/latex] = -1.360 [latex]Cr^{2+}(aq) → Cr^{3+}(aq) + e^{-}[/latex] [latex]E°_{ox}[/latex] = +0.408 [latex]Fe^{2+}(aq) → Fe^{3+}(aq) + e^{-}[/latex] [latex]E°_{ox}[/latex] = -0.769	2. Reducing agents
[latex]Fe^{2+} + Cl^{-}[/latex] : E° < 0 [latex]I_{2} + Cl^{-}[/latex]: E° < 0 [latex]Fe^{2+} + Cr^{2+}[/latex] : E° < 0 [latex]I_{2} + Cl^{2+}[/latex]: E° > 0 ✓ [latex]Fe^{2+} + Fe^{2+}[/latex] : E° < 0 [latex]I_{2} + Fe^{2+}[/latex]: E° < 0	3. Possible combinations
[latex]I_{2}(s) + 2Cr^{2+}(aq) → 2I^{-}(aq) + 2Cr^{3+}(aq)[/latex] E° = 0.942 V	4. Redox reaction

Lithium is the strongest reducing agent. O = strongest oxidizing agent; R = strongest reducing agent. Fluorine is the strongest oxidizing agent. Lithium and fluorine are very dangerous materials to work with.	AcidicSolution, $[H^{+}]$ = 1 M
	$E°_{red}$ (V)
	-3.040 -2.936 -2.906 -2.869 -2.714 -2.357 -1.680 -1.182 -0.762 -0.744 -0.409 -0.408 -0.402 -0.356 -0.336 -0.282 -0.236 -0.152 -0.141 -0.127 0.000 0.073 0.144 0.154 0.155 0.161 0.339 0.518 0.534 0.769 0.796 0.799 0.908 0.964 1.001 1.077 1.229 1.229 1.330 1.360 1.458 1.498 1.512 1.687 1.763 1.953 2.889		→Li(s) → K(s) → Ba(s) → Ca(s) →Na(s) → Mg(s) → Al(s) → Mn(s) → Zn(s) → Cr(s) → Fe(s) → $Cr^{2+}(aq)$ → Cd(s) → Pb(s) + $SO_{4}^{2-}(aq)$ → Tl(s) → Co(s) →Ni(s) → Ag(s) + $I^{-}(aq)$ → Sn(s) → Pb(s) → $H_{2}(g)$ → Ag(s) + $Br^{-}(aq)$ → $H_{2}S(aq)$ → $Sn^{2+}(aq)$ → $SO_{2}(g) + 2H_{2}O$ → $Cu^{+}(aq)$ → Cu(s) → Cu(s) → $2I^{-}(aq)$ → $Fe^{2+}(aq)$ → 2Hg(l) → Ag(s) → $Hg_{2}^{2+}(aq)$ →NO(g) + $2H_{2}O$ → $Au(s) + 4Cl^{-}(aq)$ → $2Br^{-}(aq)$ → $2H_{2}O$ → $Mn^{2+}(aq) + 2H_{2}O$ → $2Cr^{3+}(aq) + 7H_{2}O$ → $2Cl^{-}(aq)$ → $\frac{1}{2} Cl_{2}(g) + 3H_{2}O$ → Au(s) → $Mn^{2+}(aq) + 4H_{2}O$ → $PbSO_{4}(s) + 2H_{2}O$ → $2H_{2}O$ → $Co^{2+}(aq)$ → 2 $F^{-}(aq)$	$Li^{+}(aq) + e^{-}$ $K^{+}(aq) + e^{-}$ $Ba^{2+}(aq) + 2e^{-}$ $Ca^{2+}(aq) + 2e^{-}$ $Na^{+}(aq) + e^{-}$ $Mg^{2+}(aq) + 2e^{-}$ $Al^{3+}(aq) + 3e^{-}$ $Mn^{2+}(aq) + 2e^{-}$ $Zn^{2+}(aq) + 2e^{-}$ $Cr^{3+}(aq) + 3e^{-}$ $Fe^{2+}(aq) + 2e^{-}$ $Cr^{3+}(aq) + e^{-}$ $Cd^{2+}(aq) + 2e^{-}$ $PbSO_{4}(s) + 2e^{-}$ $Tl^{+}(aq) + e^{-}$ $Co^{2+}(aq) + 2e^{-}$ $Ni^{2+}(aq) + 2e^{-}$ $AgI(s) + e^{-}$ $Sn^{2+}(aq) + 2e^{-}$ $Pb^{2+}(aq) + 2e^{-}$ $2H^{+}(aq) + 2e^{-}$ $AgBr(s) + e^{-}$ $S(s) + 2H^{+}(aq) + 2e^{-}$ $Sn^{4+}(aq) + 2e^{-}$ $SO_{4}^{2-}(aq) + 4H^{+}(aq) + 2e^{-}$ $Cu^{2+}(aq) + e^{-}$ $Cu^{2+}(aq) + 2e^{-}$ $Cu^{+}(aq) + e^{-}$ $I_{2}(s) + 2e^{-}$ $Fe^{3+}(aq) + e^{-}$ $Hg_{2}^{2+}(aq) + 2e^{-}$ $Ag^{+}(aq) + e^{-}$ $2Hg^{2+}(aq) + 2e^{-}$ $NO_{3}^{-}(aq) + 4H^{+}(aq) + 3e^{-}$ $AuCl_{4}^{-}(aq) + 3e^{-}$ $Br_{2}(l) + 2e^{-}$ $O_{2}(g) + 4H^{+}(aq) + 4e^{-}$ $MnO_{2}(s) + 4H^{+}(aq) + 2e^{-}$ $Cr_{2}O_{7}^{2-}(aq) + 14H^{+}(aq) + 6e^{-}$ $Cl_{2}(g) + 2e^{-}$ $ClO_{3}^{-}(aq) + 6H^{+}(aq) + 5e^{-}$ $Au^{3+}(aq) + 3e^{-}$ $MnO_{4}^{-}(aq) + 8H^{+}(aq) + 5e^{-}$ $PbO_{2}(s) + SO_{4}^{2-}(aq) + 4H^{+}(aq) + 2e^{-}$ $H_{2}O_{2}(aq) + 2H^{+}(aq) + 2e^{-}$ $Co^{3+}(aq) + e^{-}$ $F_{2}(g) + 2e^{-}$
	Basic Solution, $[OH^{-}]$ = 1 M
	$E°_{red}$ (V)
	-0.891 -0.828 -0.547 -0.445 -0.140 0.004 0.398 0.401 0.614 0.890	→ Fe(s) + 2 $OH^{-}$ (aq) → $H_{2}(g)$ + 2 $OH^{-}$ (aq) → $Fe(OH)_{2}(s)$ + $OH^{-}$ (aq) → $S^{2-}(aq)$ →NO(g) + 4 $OH^{-}$ (aq) → $NO_{2}^{-}$ (aq) + 2 $OH^{-}$ (aq) → $ClO_{3}^{-}$ (aq) + 2 $OH^{-}$ (aq) → 4 $OH^{-}$ (aq) → $Cl^{-}(aq)$ + 6 $OH^{-}$ (aq) → $Cl^{-}(aq)$ + 2 $OH^{-}$ (aq)		$Fe(OH)_{2}(s) + 2e^{-}$ $2H_{2}O + 2e^{-}$ $Fe(OH)_{3}(s) + e^{-}$ $S(s) + 2e^{-}$ $NO_{3}^{-}(aq) + 2H_{2}O + 3e^{-}$ $NO_{3}^{-}(aq) + H_{2}O + 2e^{-}$ $ClO_{4}^{-}(aq) + H_{2}O + 2e^{-}$ $O_{2}(g) + 2H_{2}O + 4e^{-}$ $ClO_{3}^{-}(aq) + 3H_{2}O + 6e^{-}$ $ClO^{-}(aq) + H_{2}O + 2e^{-}$

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