Chem 162-2010 homework 13th week

Chem 162-2010 homework 13th week - Chem 162-2010 Hill &...

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Unformatted text preview: Chem 162-2010 Hill & Petrucci Homework Chapter 18 E o cell and the Spontaneity of Redox Reactions Use data from Table 18.1 and Appendix C, as necessary. 43. Predict whether a spontaneous reaction will occur in the forward direction in each of the following. Assume that all reactants and products are in their standard states. (a) Sn 4+ (aq) + 2I- (aq) → Sn 2+ (aq) + I 2 (s) Sn 4+ + 2e- → Sn 2+ 0.154V 2I- → I 2 + 2e--0.535V Sn 4+ (aq) + 2I- (aq) → Sn 2+ (aq) + I 2 (s)-0.381; therefore non-spontaneous (b) 2MnO 2 (s) + 3ClO- (aq) + 2OH- (aq) → 2MnO 4- (aq) + 3Cl- (aq) + H 2 O(l) 2(MnO 2 (s) + 2H 2 O → MnO 4- (aq) + 4H + + 3e- )-1.70 3(ClO- (aq) + H 2 O + 2e- → Cl- (aq) + 2OH- ) +0.890 2MnO 2 (s) + 4H 2 O + 3ClO- (aq) + 3H 2 O → 2MnO 4- (aq) + 8H + + 3Cl- (aq) + 6OH--0.81, non-spontaneous 2MnO 2 (s) + 4H 2 O + 3ClO- (aq) + 3H 2 O → 2MnO 4- (aq) + 2H + + 3Cl- (aq) + 6H 2 O 2MnO 2 (s) + H 2 O + 3ClO- (aq) → 2MnO 4- (aq) + 2H + + 3Cl- (aq) 2MnO 2 (s) + H 2 O + 3ClO- (aq) + 2OH- → 2MnO 4- (aq) + 2H + + 2OH- + 3Cl- (aq) 2MnO 2 (s) + 3ClO- (aq) + 2OH- → 2MnO 4- (aq) + H 2 O + 3Cl- (aq) The above is incorrect because it shows the MnO2 half-cell reaction as taking place in an acidic solution; yet, the total reaction takes place in basic solution. So this is inconsistent. Therefore, find an MnO2 reaction, if possible, that takes place in a basic solution. (b) 2MnO 2 (s) + 3ClO- (aq) + 2OH- (aq) → 2MnO 4- (aq) + 3Cl- (aq) + H 2 O(l) 2(MnO 2 (s) + 4OH- → MnO 4- (aq) + 2H 2 O + 3e- )-0.60 3(ClO- (aq) + H 2 O + 2e- → Cl- (aq) + 2OH- ) +0.890 +0.29, spontaneous 45. Predict whether each of the following processes will proceed in the forward direction to any appreciable extent. (a) the reduction of Sn 4+ (aq) to Sn 2+ (aq) by Cu(s) Sn 4+ (aq) + 2e- → Sn 2+ (aq) +0.154 Cu → Cu2+ + 2e--0.34-0.19 not spontaneous, to any extent. (b) the oxidation of I 2 (s) to IO 3- (aq) by O 3 (g) in acidic solution I 2 + 6H 2 O → 2IO 3- + 12H + + 10e--1.20 O 3 + 2H + + 2e- → O 2 + H 2 O +2.075 +0.88; therefore, spontaneous (c) the oxidation of Cr(OH) 3 (s) to CrO 4 2- (aq) by H 2 O 2 in basic solution Cr(OH) 3 (s) → CrO 4 2- Voltages are not available in Table 18.1 or Appendix c for this half-cell reaction. 47. Silver does not react with HCl(aq), but it does react with HNO 3 (aq). (a) Explain the difference in the behavior of silver toward these two acids. (b) Write a plausible net ionic equation for the reaction of silver with HNO 3 (aq). 1 Ag → Ag + + 1e--0.800V 2Cl- → Cl 2 + 2e--1.358V Silver can only be oxidized. Cl- can only be oxidized. Hence, there is no redox reaction for this combination. However, while Ag can be oxidized, NO 3- can be reduced. Hence, there is a redox reaction between these two substances....
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This document was uploaded on 11/02/2011 for the course GEN CHEM 162 at Rutgers.

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Chem 162-2010 homework 13th week - Chem 162-2010 Hill &...

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