Google for "solubility rules"
Basically, when you have these kinds of reactions you have a solution of ions (Ba 2+ and OH -) added to another solution of ions (H+ and SO4 2-). In a way, you could say the default thing is that nothing happens when you mix the two solutions (you just get a bigger solution of all these ions floating around). But that's where the solubility rules come in.
If you look at a standard set of chemistry solubility rules you'll see that some salts (metal + non-metal) are insoluble (stays solid in water). For example, the rules say that most sulfates (SO4 2-) are soluble, with the exception of Barium Sulfate (BaSO4) and others. Therefore, if you mix the two solutions, everything will stay aqueous except for combinations that are insoluble. Thus in this case, Ba 2+ will combine with SO4 2- to form the solid BaSO4. Also, H+ and OH- will form the liquid H20. Just have to remember H+ and OH- do that.
Thus the net equation is Ba(OH)2(aq) + H2SO4(aq) -> 2H20(l) + BaSO4(s)
Basically, when you have these kinds of reactions you have a solution of ions (Ba 2+ and OH -) added to another solution of ions (H+ and SO4 2-). In a way, you could say the default thing is that nothing happens when you mix the two solutions (you just get a bigger solution of all these ions floating around). But that's where the solubility rules come in.
If you look at a standard set of chemistry solubility rules you'll see that some salts (metal + non-metal) are insoluble (stays solid in water). For example, the rules say that most sulfates (SO4 2-) are soluble, with the exception of Barium Sulfate (BaSO4) and others. Therefore, if you mix the two solutions, everything will stay aqueous except for combinations that are insoluble. Thus in this case, Ba 2+ will combine with SO4 2- to form the solid BaSO4. Also, H+ and OH- will form the liquid H20. Just have to remember H+ and OH- do that.
Thus the net equation is Ba(OH)2(aq) + H2SO4(aq) -> 2H20(l) + BaSO4(s)
