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Balance the following equation by oxidation number method. KMnO_(4)+H_(2)SO_(4)+H_(2)C_(2)O_(4)toK_(2)SO_(4)+MnSO_(4)+CO_(2)+H_(2)O |
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Answer» Solution :Step 1. The given equation is `KMnO_(4)+H_(2)SO_(4)+H_(2)C_(2)O_(4)toK_(2)SO_(4)+MnSO_(4)+CO_(2)+H_(2)O` WRITING the OXIDATION numbers of all atoms, we have `overset(+1+7-2)(KMnO_(4))+overset(+1+6-2)(H_(2)SO_(4))+overset(+1+3-2)(H_(2)C_(2)O_(4))tooverset(+1+6-2)(K_(2)SO_(4))+overset(+2+6-2)(MnSO_(4))+overset(+4-2)(CO_(2))+overset(+1-2)(H_(2)O)` Step 3 : The atoms showing change in oxidation number are Mn (from + 7 to + 2) and C (from +3 to +4). Thus, `KMnO_(4)` is the oxidising AGENT and `H_(2)C_(2)O_(4)` is the reducing agent. Step 4. The atoms of Mn are equal on both sides. In order to equalise the atoms of `C,CO_(2)` should be multiplied by 2. Therefore, we have `KMnO_(4)toH_(2)SO_(4)+H_(2)C_(2)O_(4)toK_(2)SO_(4)+MnSO_(4)+2CO_(2)+H_(2)O` Step 5. In `KMnO_(4)`, an atom of Mn should gain 5 electrons to decrease its oxidation number from +7 to +2, and in `H_(2)C_(2)O_(4)` each atom of C should lose one electron to increase its oxidation state from +3 to +4.Therefore, `underset(5e^(-))underset(uarr)(KMnO_(4))+H_(2)SO_(4)+underset(1e^(-))underset(darr)(H_(2)C_(2)O_(4))toK_(2)SO_(4)+2MnSO_(4)+2CO_(2)+H_(2)O` Total number of electrons gained by 1 atom of Mn = 5. Total number of electrons lost by 2 atoms of `C=1xx2=2`. Step 6.In order to equalise the total electrons gained and total electrons lost, `KMnO_(4)` should be multiplied by 2 and `H_(2)C_(2)O_(4)` by 5. Hence, the coefficient for Mn is 2 and that for C is 5. Step 7. Multiplying KMnO4 and MnSO4 by coefficient 2 and multiplying `H_(2)C_(2)O_(4)` and `CO_(2)` by coefficient 5, we have `2KMnO_(4)+H_(2)SO_(4)+5H_(2)C_(2)O_(4)toK_(2)SO_(4)+2MnSO_(4)+10CO_(2)+H_(2)O` Balancing the above equation with respect to atoms other than H and O, we have `2KMnO_(4)+3H_(2)SO_(4)+5H_(2)C_(2)O_(4)toK_(2)SO_(4)+2MnSO_(4)+10CO_(2)+H_(2)O` On balancing H and 0, we get the final balanced equation. `2KMnO_(4)+3H_(2)SO_(4)+5H_(2)C_(2)O_(4)toK_(2)SO_(4)+2MnSO_(4)+10CO_(2)+8H_(2)O` |
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