How do I find the overall net reaction that occurs in this 2 part reaction?

Na2CO3(aq) + HCl(aq) -> HCO3(aq) + NaCl(aq)
HCO3(aq) + HCl(aq) -> H2CO3(aq) + NaCl (aq)

basically what you do is add them up. for example you have 2 HCl on the left hand side (one from each equation) and two NaCl on the other side so you will end up with...

Na2CO3(aq) + 2HCl(aq) + HCO3(aq)-> HCO3(aq) + 2NaCl(aq) + H2CO3(aq)

the common species on each side then cancel out. in this case there is a HCO3(aq) on both sides. once you cross them out you have your final equation.

Na2CO3(aq) + 2HCl(aq) 2NaCl(aq) + H2CO3(aq)

Hope this helps

Come on!   easy.  

Reaction pt1 produces an intermediate compound that is sodium bicarbonate   NaHCO3 as you add HCl.     Reaction 2 does not proceed until all carbonate Na2CO3 is transformed into bicarbonate.   Then, if you continue addin HCl  the resulting bicarbonate starts to react until depleted and transformed into carbonic acid.   So, you can simply add both reactions, sum equal compounds in the same side of the resulting reaction and cancel equal elements in different sides of the reaction  (Keeping an eye on stoichiometry).


Na2CO3 + HCl + NaHCO3 + HCl = NaHCO3 + NaCL + H2CO3 + NaCl

Then

Na2CO3 + 2HCl = H2CO3 + 2NaCl