Hi
Homework questions?
First one shows the way. On the left side you have the inputs: zinc and hydrochloric acid.
On the right side, the outputs: Zinc chloride and hydrogen gas.
The challenge is to find the right nubers pf atoms that can satisfy each side.
Hydrogen gas (on the right) needs two atoms: H2
So you need two atoms of hydrogen on the left:
Zn + 2HCl = ZnCl2 + H2
The number of atoms on each side of the equation is balanced.
The next one is iron rusting
2Fe + O2 = Fe2O3 doesn't work, because the oxygens do not match on left and right.
So we have to modify it thus:
4Fe + 3O2 = 2Fe2O3 (4 atoms of Fe; 6 of oxygen on each side)
Up to you to solve the rest :)