Answer the following questions in detail.

Question

Using the oxidation number method write the net ionic equation for the reaction of potassium permanganate, $KMnO _4$, with ferrous sulphate, $FeSO _4$.
$
MnO _{4( aq )}^{-}+ Fe _{( aq )}^{2+} \longrightarrow Mn _{( aq )}^{2+}+ Fe _{( aq )}^{3+}
$

Vidyadip · Accepted Answer

Step 1: Write skeletal equation and balance the elements other than $O$ and $H$.
$
MnO _{4( aq )}^{-}+ Fe _{( aq )}^{2+} \longrightarrow Mn _{( aq )}^{2+}+ Fe _{( aq )}^{3+}
$
Step 2: Assign oxidation number to $Mn$ and $Fe$, and calculate the increase and decrease in the oxidation number and make them equal.

To make the net increase and dicrease equal, we must take 5 atoms of $Fe ^{2+}$
$
MnO _{4( aq )}^{-}+5 Fe _{( aq )}^{2+} \longrightarrow Mn _{( aq )}^{2+}+5 Fe _{( aq )}^{3+}
$
Step 3: Balance the 'O' atoms by adding $4 H _2 O$ to the right-hand side.
$
MnO _{4( aq )}^{-}+5 Fe _{( aq )}^{2+} \longrightarrow Mn _{( aq )}^{2+}+5 Fe _{( aq )}^{3+}+4 H _2 O _{(l)}
$
Step 4: The medium is acidic. To make the charges and hydrogen atoms on the two sides equal, add $8 H ^{+}$on the left-hand side.
$
MnO _{4( aq )}^{-}+5 Fe _{( aq )}^{2+}+8 H _{( aq )}^{+} \longrightarrow Mn _{( aq )}^{2+}+5 Fe _{( aq )}^{3+}+4 H _2 O _{(l)}
$
Step 5: Check the two sides for balance of charges and atoms. The net ionic equation obtained in step 4 is the balanced equation.
Hence, balanced equation:
$
MnO _{4( aq )}^{-}+5 Fe _{( aq )}^{2+}+8 H _{( aq )}^{+} \longrightarrow Mn _{( aq )}^{2+}+5 Fe _{( aq )}^{3+}+4 H _2 O _{(l)}
$

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