1) for a given reaction to consume one reactant completely, must the equivalents of both reactants be same? for example, I know in the reaction of HCl + NaOH - the equivalents of HCl=equivalents of NaOH for a titration, is it the same for Na2CO3 + HCl?
2) the following is an excerpt from my textbook-
Double titration: This is a titration of specific compound using different indicators. When the solution containing NaOH and Na2CO3 is titrated using phenolpthalein indicator, the following reaction takes place at the phenolpthalein end point.
NaOH + HCl - NaCl + H2O
Na2CO3 + HCl - NaHCO3 + NaCl
Here, Equivalents of NaOH + 1/2 equivalents of Na2CO3= equivalents of HCl...(i)
When methyl orange is used Na2CO3 is converted into NaCl + CO2 + H2O
Hence equivalents of NaOH + eqs. of Na2CO3=eqs. of HCl...(ii)
I dont't understand how we got the first equation and this titration in general, can someone please explain?