[AlphaHelix]

so i commited to an experiment where i titrated a 0.1000 M solution of HCl with a 0.1000 M of HCl. what i need to find is the concentration of H+ vs my concentration of HCl. (i am finding percent dissociation. i collected pH data and i found it's equivalence point at 6.58 pH. so i found that it's hydronium concentraton is 2.63 x 10^-7 at it's equivalence point. now i just need my HCl concentration. so now i have a pKa value of 6.58 (pKa = pH at equivalence point) making it's Ka value the same as that of my pH 2.63 x 10^-7. so now that i have my Ka value and my hydronium value i was considering making an "ICE" box to find my HA value but this is my conundrum:
                    HCl + NaOH -> H2O + NaCl
with this kind of equation i am working with my Ka should be NaCl/[HCl][NaOH]. but my Ka should look like this: Ka = [H+][A-]/[HA]. in the equation above i don't even know where to put my calculated hydronium value. i am so lost. basically my overall question is: how do i find my HCl concentration from my Ka and hydronium values?

[XGen]

Instead of having HCl + NaOH -> H₂O + NaCl, try writing a net ionic equation.

[AlphaHelix]

Instead of having HCl + NaOH -> H₂O + NaCl, try writing a net ionic equation.

okay but i don't know what that is

[Borek]

You are wrong in so many aspects I have no idea where to start.

First of all - what are you trying to determine?

Hydrochloric is a very strong acid, which means it is always 100% dissociated. Depending on the source its dissociation constant is listed as 10³-10⁷. There is no accurate value, because it is very difficult to determine Ka of such a strong acid experimentally. For sure it can't be done by a simple titration.

(pKa = pH at equivalence point)

No, that's not true. pKa = pH at HALF equivalence, when exactly 50% of the acid is neutralized. But it works only for weak acids, not for a strong acid like HCl.