Question

Complete and balance the following skeleton reaction and identify the oxidizing and reducing agents. Include the states of all reactants and products in your balanced equation. You do not need to include the states with the identities of the oxidizing and reducing agents. CrO^2-_4 (aq) + Cu(s) rightarrow Cr(OH)_3 (s) + Cu(OH)_2(s) [basic] The oxidizing agent is The reducing agent is

Answer 1

Split in half cells

CrO4-2 = Cr(OH)3

Cu = Cu(OH)2

balance O

CrO4-2 = Cr(OH)3 + H2O

2H2O + Cu = Cu(OH)2

balance H

5H+ + CrO4-2 = Cr(OH)3 + H2O

2H2O + Cu = Cu(OH)2 + 2H+

balance charges

3e- + 5H+ + CrO4-2 = Cr(OH)3 + H2O

2H2O + Cu = Cu(OH)2 + 2H+ +2e-

balance e-

6e- + 10H+ + 2CrO4-2 =2 Cr(OH)3 + 2H2O

6H2O + 3Cu = 3Cu(OH)2 + 6H+ + 6e-

add all

6H2O + 3Cu + 6e- + 10H+ + 2CrO4-2 =2 Cr(OH)3 + 2H2O + 3Cu(OH)2 + 6H+ + 6e-

cancel common terms

4H2O(l) + 3Cu(s) + 4H+(aq) + 2CrO4-2(aq) = 2Cr(OH)3(s) + 3Cu(OH)2(s)

in basic solution, add OH-

4OH- + 4H2O(l) + 3Cu(s) + 4H+(aq) + 2CrO4-2(aq) = 2Cr(OH)3(s) + 3Cu(OH)2(s) + 4OH-

8H2O(l) + 3Cu(s) + 2CrO4-2(aq) = 2Cr(OH)3(s) + 3Cu(OH)2(s) + 4OH-

now,

from the reaction

oxidizing agent --> reduces --> gains electrons --> CrO4-2(aq)

reducing agnet --> oxidizes --> losses electorns ---> Cu(s)