Answer: The first reaction is a single replacement reaction
Fe + CuSO4 => FeSO4 + Cu
Note the charges are indicated in the chemical reaction. SO4 is -2, so Fe is 2+ same with copper
2. Is a double replacement reaction
KCl + Hg2SO4 => K2SO4 + HgCl
Balance then chemical reaction
2 KCl + Hg2SO4 => K2SO4 + 2HgCl
K has a +1 oxidation, Cl is -1, Hg is +1, SO4 has a -2 oxidation
3. Is a synthesis reaction
S + O2 => SO2
Step-by-step explanation: