For a complete neutralization between \(HCl\) and \(Na _{2} CO _{3}\), methylorange is used
\(2 HCl + Na _{2} CO _{3} \rightarrow 2 NaCl + H _{2} O + CO _{2}\)
It must be noted that if the reaction were to be partial, the salt produced will not be \(NaCl\) alone, it will be a mixture of \(NaCl\) and \(NaHCO _{3}\) and phenolphthalein is used as the indicator
\(HCl + Na _{2} CO _{3} \rightarrow NaHCO _{3}+ NaCl\)