Question

Consider the following standard reduction potentials in acid solution: The weakest reducing agent listed above is Co Cr Cr3 Mn2 MnO4-

Answer 1

This is an complete question, here is a complete question.

Consider the following standard reduction potentials in acid solution:

$Cr^{3+}+3e^-\rightarrow Cr$      $E^o=-0.74V$

$Co^{2+}+2e^-\rightarrow Co$    $E^o=-0.28V$

$MnO_4^-+8H^++5e^-\rightarrow Mn^{2+}+4H_2O$    $E^o=+1.51V$

The weakest reducing agent listed above is:

(a) $Cr^{3+}$  

(b) $Cr$  

(c) $Mn^{2+}$

(d) $MnO_4^-$

Answer : The correct option is, (d) $MnO_4^-$

Explanation :

As we know that,

The substance having highest positive $E^o$ potential will always get reduced and will undergo reduction reaction and weakest reducing agent or strongest oxidizing agent.

From the standard reduction potentials we conclude that,

$MnO_4^-$ having highest positive $E^o$ potential than the other. So, it will always get reduced and will undergo reduction reaction and weakest reducing agent.

Hence, the correct option is, (d) $MnO_4^-$