Final answer:
To find the concentration of HCl, we calculate the moles of NaOH used (0.0221 L × 0.142 M = 0.0031392 mol), knowing that the reaction with HCl is 1:1. Then, dividing the moles of HCl by its volume (0.0031392 mol / 0.025 L), we arrive at the concentration of HCl, which is 0.1256 M.
Step-by-step explanation:
To calculate the concentration of HCl, we use the titration method, which is a process where a solution of known concentration is used to determine the concentration of an unknown solution. In this case, we are given that 25 ml of HCl is neutralized by 22.1 ml of 0.142 M NaOH. The reaction between HCl and NaOH is a 1:1 stoichiometry as shown in the balanced equation:
HCl + NaOH → NaCl + H₂O
First, we need to calculate the number of moles of NaOH used in the titration to reach the end point:
moles of NaOH = volume (L) × molarity = 0.0221 L × 0.142 M = 0.0031392 mol
Since the stoichiometry is 1:1, this is also the number of moles of HCl neutralized. Next, to find the concentration of HCl, we divide the moles of HCl by the volume of HCl in liters:
concentration of HCl = moles of HCl / volume of HCl (L) = 0.0031392 mol / 0.025 L = 0.125568 M
Therefore, the concentration of the HCl solution is 0.1256 M (rounded to four significant figures).