To calculate the concentration of the HCl solution using the provided titration data.

The problem asks to calculate the concentration of the HCl solution using the provided titration data.

Step 1: Write the balanced chemical equation for the reaction between HCl and Na₂CO₃.
The reaction between hydrochloric acid (HCl) and sodium carbonate (Na₂CO₃) is:

$$2\text{HCl}(aq) + \text{Na}_2\text{CO}_3(aq) \to 2\text{NaCl}(aq) + \text{H}_2\text{O}(l) + \text{CO}_2(g)$$

From the balanced equation, the stoichiometric ratio of HCl to Na₂CO₃ is $2:1$.
Therefore, the number of moles of acid ($n