# Can the concentration of a sodium carbonate solution be determined using volumetric analysis?

In the titration of sodium carbonate with hcl , isn't the first end point determined by phenol phthalene is equivalent to the volume of sodium carbonate

because my text book say thats the volume at the first end point is just half the sodium carbonate and the seconds end point is the whole sodium carbonate.

I know that at the first end point all the sodium carbonate all be converted to sodium bicarbonate but why shouldn't i stop here?!

$\ce{Na2CO3(aq) + HCl(aq) → NaHCO3(aq) + NaCl(aq)}$
$\ce{NaHCO3(aq) + HCl(aq) → NaCl(aq) + CO2(g) + H2O(l) }$