Question

Why is n factor of na2co3 is tken as 2 and nahco3 as 1 with hcl?

Answer 1

Explanation:

A sample contains NaOH, Na2CO3& NaHCO3. This solution is titrated with HCl or H2SO4

(i) When phenolphthalein (HPh) is used as indicator the reaction are given below.

Na2CO3 + HCl → NaHCO3 + NaCl

This is the half neutralization of Na2CO3

NaHCO3 + HCl → X

NaOH + HCl → NaCl + H2O

Hence

Meq. Of HCl = Meq. Of NaOH + (1/2) Meq. Of Na2CO3

(ii) When methyl orange (MeOH) is used as indicator

Na2CO3 + 2HCl → 2NaCl + H2O + CO2

This is the complete neutralization

NaHCO3 + HCl → NaCl + H2O + CO2

NaOH + HCl → NaCl + H2O

in this case

Meq. Of HCl = Meq. Of NaOH + Meq. Of Na2CO3 + Meq. Of NaHCO3

(iii) If MeOH is added after the first end point obtained from HPh

NaHCO3 + NaHCO3 + HCl → NaCl + H2O + CO2

Produced original

Meq. Of HCl = Meq. Of NaHCO3 (produced) + Meq. Of NaHCO3 (original)