balance the following redox reaction if it occurs in acidic solution. what are t

Question

balance the following redox reaction if it occurs in acidic solution. what are the coefficients in front of MnO2 and H2O MnO4^- + CN^- ===> MnO4 + CNO^-
a) 2 MnO2 ; 2 H2O b) 2 MnO2 ; H2O c) 3 MnO2 ; 2 H2O d) MnO2 ; H2O balance the following redox reaction if it occurs in acidic solution. what are the coefficients in front of MnO2 and H2O MnO4^- + CN^- ===> MnO4 + CNO^-
a) 2 MnO2 ; 2 H2O b) 2 MnO2 ; H2O c) 3 MnO2 ; 2 H2O d) MnO2 ; H2O MnO4^- + CN^- ===> MnO4 + CNO^-
a) 2 MnO2 ; 2 H2O b) 2 MnO2 ; H2O c) 3 MnO2 ; 2 H2O d) MnO2 ; H2O

Explanation / Answer

The balance reaction is as follows:

3 CN- + 2 MnO4- + H2O = 3 CNO- + 2 MnO2 + 2 OH-

Thus the correct answer is b) 2 MnO2 ; H2O

First CN- reacts with H2O as follows:

CN- + H2O = CNO- + 2 H+ + 2e-                         …1

Mno4- ion reduce to MnO2 as follows:

MnO4- + 4 H+ + 3e- = MnO2 + 2 H2O                         …2

Now multiply the eq.1 by 3 and eq 2 by 2 and then add :

3(CN- + H2O = CNO- + 2 H+ + 2e-)

= 3CN- + 3H2O = 3CNO- + 6 H+ + 6e-

2(MnO4- + 4 H+ + 3e- = MnO2 + 2 H2O)= 2MnO4- + 8 H+ + 6e- = 2MnO2 + 4H2O

2MnO4- + 8 H+ + 6e- = 2MnO2 + 4H2O

3CN- + 3H2O = 3CNO- + 6 H+ + 6e-

3 CN- + 2 MnO4- + H2O = 3 CNO- + 2 MnO2 + 2 OH-

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