In the case of phenolphthalein as indicator only Na2CO3 reacts with HCl to give NaHCO3
Na2CO3+HCl→NaHCO3+NaCl
25ml 12ml and 120N
mmole of Na2CO3 in 25ml= mmole of HCl=12×120=0.6
wt106×1000=0.6
Wt of Na2CO3 in 25ml=0.6×1061000=0.0636g
Wt of Na2CO3 in 1 lit =0.063625×1000=2.544g
In the presence of methyl orange as indicator:
Na2CO3+2HCl→2NaCl+H2O+CO2
NaHCO3+HCl→NaCl+H2O+CO2
meq of Na2CO3+ meq. of NaHCO3= meq of HCl
2×mmole of Na2CO3+mmole of NaHCO3=mmole of HCl
2×0.6+ mmole of NaHCO3=30×120×1
mmole of NaHCO3=1.5−1.2=0.3
wt.ofNaHCO384×1000=0.3
wt of NaHCO3 in 25ml=0.3×841000=0.0252
wt of NaHCO3 in 1 lit =0.025225×1000=1.008g