Answer:
Pb(NO3)2+ 2Kl →PbI2 + 2KNO3
Mg + 2HCl → MgCl2 + H2
4H2O → 4H^+ + 4OH^-
2Mg + O2 → 2MgO
Explanation:
This question has to do with the balancing of chemical reaction equations. The general rule for balancing chemical reaction equation is that the number of atoms of each element on the left hand side of the reaction equation must be equal to the number of atoms of the same element on the right hand side of the reaction equation.
This principle was followed in balancing each reaction equation above. For instance, in the burning of magnesium, there are two atoms of both magnesium and oxygen on either side of the reaction equation.