Question

Cr2O7²- + C2H4O→C2H4O2 + Cr3+
balance the following equation by ion electron method​

Answer 1

The unbalanced redox equation is as follows:
Cr
2
​
O
7
2−
​
+C
2
​
H
4
​
O+H
+
→C
2
​
H
4
​
O
2
​
+Cr
3+


Balance all atoms other than H and O.
Cr
2
​
O
7
2−
​
+C
2
​
H
4
​
O+H
+
→C
2
​
H
4
​
O
2
​
+2Cr
3+


The oxidation number of Cr changes from 6 to 3. So the change in oxidation number of one Cr atom is 3.
For 2 Cr atoms, the oxidation number changes by 6.

The oxidation number of C changes from -1 to 0. So the change in oxidation number of 1 C atom is 1.
For 2 C atoms, the oxidation number changes by 2.

The increase in the oxidation number is balanced with decrease in the oxidation number by multiplying
C
2
​
H
4
​
O and C
2
​
H
4
​
O
2
​
with 3.
Cr
2
​
O
7
2−
​
+3C
2
​
H
4
​
O+H
+
→3C
2
​
H
4
​
O
2
​
+2Cr
3+


O atoms are balanced by adding 4 water molecules on RHS.
Cr
2
​
O
7
2−
​
+3C
2
​
H
4
​
O+H
+
→3C
2
​
H
4
​
O
2
​
+2Cr
3+
+4H
2
​
O

Hydrogen atoms are balanced by adding 7 H
+
atoms on RHS.
Cr
2
​
O
7
2−
​
+3C
2
​
H
4
​
O+8H
+
→3C
2
​
H
4
​
O
2
​
+2Cr
3+
+4H
2
​
O

This is the balanced chemical equation.
Hope this helps you.....