30. Complete and balance the following chemical equations :
(a) NaCl (aq) + H2O (1)
Electricity
Heat
(b) NaHCO3
(c) NaCl + NH3
+ NH3 + H2O + CO2 ->
(d) Ca(OH)2 + Cl2----
Answers
Explanation:
The complete, unbalanced chemical equation is :
MnO
4
−
+H
2
O+I
−
→MnO
2
+IO
3
−
I atoms and Mn atoms are balanced.
The oxidation number of iodine increases from −1 (in I
−
) to +5 (in IO
3
−
). Total increase in oxidation number for iodine is +5−(−1)=6.
The oxidation number of Mn decreases from +7 (in MnO
4
−
) to +4 (in MnO
2
). Total decrease in oxidation number for Mn is 7−4=3.
To balance the total increase in oxidation number with the total decrease in oxidation number, add coefficient 2 to Mn species.
2MnO
4
−
+H
2
O+I
−
→2MnO
2
+IO
3
−
Balance O atoms by adding 2 water molecules to the products side.
2MnO
4
−
+H
2
O+I
−
→2MnO
2
+IO
3
−
+2H
2
O
One water molecule cancels on each side.
2MnO
4
−
+I
−
→2MnO
2
+IO
3
−
+H
2
O
Balance H atoms by adding 2 protons to the reactants side.
2MnO
4
−
+I
−
+2H
+
→2MnO
2
+IO
3
−
+H
2
O
This is the complete balanced chemical equation