Since Na2CO3+2HCl-->CO2+H2O+2NaCl 1 mole of NaCO3reacts with 2 mole of HCl no. of mole of Na2CO3=molarity * volume(in dm3) =25*10-3mole So that no. of mole of HCl= no. of mole of Na2CO3* 2 =5*10-3 volume of HCl used = no. of mole of HCl / molarity of HCl if you...