Given the reaction:
ba(oh)2(aq) + h2so4(aq) --> baso4(s) + 2 h2o(l) + energy
as the barium hydroxide solution is added to the solution of sulfuric acid, the electrical conductivity of the acid solution decreases because the
(1) volume of the reaction mixture increases
(2) temperature of the reaction mixture decreases
(3) concentration of ions increases
(4) concentration of ions decreases