This is a single replacement reaction in which iron replaces copper from its salt solution. As iron is more reactive than copper , it easily loses electrons to convert to in and in accepts electrons to form .
The equation is also balanced as equal number of atoms of each element are present on reactant and product side.
1. : The equation is not balanced.
2. : This is a double displacement reaction and is balanced.
4. : This is a double displacement reaction and is not balanced.