42.Complete the equation.
a) Zn +02 -
b) C+02 -
Answers
Answer:
1) Zn + O2 = ZnO2
2) C + O2 = CO2
Answer:
MnO
4
−
+C
2
O
4
2−
+H
+
→Mn
2+
+2CO
2
+H
2
O
The oxidation number of Mn decreases from +7 to +2.
The decrease in the oxidation number is 7−2=5
The oxidation number of C increases from +3 to +4.
The increase in the oxidation number for 1 C atom is 4−3=1
The increase in the oxidation number for 2 C atom is 2×1=2
To balance the increase in the oxidation number with decrease in the oxidation number, multiply Mn containing species with 2 and C containing species with 5.
2MnO
4
−
+5C
2
O
4
2−
→2Mn
2+
+10CO
2
Balance O atoms by adding 8 water molecules to the products side.
2MnO
4
−
+5C
2
O
4
2−
→2Mn
2+
+10CO
2
+8H
2
O
Balance H atoms by adding 16 H
+
ions to the reactants side.
2MnO
4
−
+5C
2
O
4
2−
+16H
+
→2Mn
2+
+10CO
2
+8H
2
O
This is the balanced equation.