text: im confused, why is there never a 100% yield in chemistry?   all reactions are going both ways.  for instance, h2 + o2--->h2o ( i know it's not balanced) also goes from h2o---->h2 + o2.  a 100% yield is never acheived because the reaction reaches a state of equilibrium where the reactants are going from h2 + o2--->h2o just as fast as they are going from h2o--->h2 + o2.  an entire semester of inorganic chemistry is devoted to the concept of equalibrium.