Chemistry Addition Problem?

[B.B.]

Well you can't just make whatever you want to while "adding" molecules. For instance 2H2O --> H2 + O2 is balanced, but it won't happen in real life without electrolysis, but that's another topic. Usually you're given a chemical equation i.e. H2O + SO2 --> H2SO4 , and you have to add coefficients to the different molecules to make there be equal amounts of each elements on both sides. That equation isn't balanced because there is 3 oxygen molecules on the left and 4 on the right. This is a horrible example because it cant be done in one equation. A "good" example is: NO + O2 --> NO2 as you can see, this equation isn't balanced because there are 3 atoms of oxygen on the left side and only 2 on the second. To balance it:
2NO + O2 --> 2NO2

[lawnmowjob]

there's types of reactions

single displacement
synthesis
double displacement
combustion
redox

and many more

which you can search up