If i titrated 25.0mL of 0.500M HCl with 0.500M NaOH and then 25.0mL of 0.500M of an unknown weak acid HA with 0.500M NaOH. How would the two titration curves compare at 10 or 15mL of NaOH Beyond equivelance pts? I think that they will be the ssame or similar but i don't know how to explain why ...
I can't draw on this forum how these things look; however, remember that with the HA, adding NaOH produces a buffered solution. Because it's a weak acid the initial pH (before any NaOH is added) is higher and the addition of NaOH forms NaA. The mixture of unreacted HA and the NaA formed produces a buffer. The vertical part of the titration curve is shortened and the pH at the equivalence point is higher (7.0 with HCl and about 8.5 with HA). The pH after the equivalence point is essentially unchanged between the two. You can go to google and type in titration curves or something like that and get pictures of how they look. If you can't find them, repost and I'll look.
The two titration curves for the titration of HCl and the unknown weak acid HA with NaOH will not be the same or similar beyond the equivalence points due to the differences in their acid-base properties.
Here's an explanation why:
1. HCl titration:
HCl is a strong acid, meaning it ionizes completely in water, releasing H+ ions. Consequently, the pH of the solution will decrease rapidly as NaOH is added until it reaches the equivalence point, where the moles of H+ ions in the solution are equal to the moles of OH- ions added. Beyond the equivalence point, the excess OH- ions from the NaOH will increase the pH of the solution, resulting in a steep rise in the titration curve.
2. Unknown weak acid HA titration:
The unknown weak acid HA does not ionize completely in water and exists in equilibrium with its conjugate base A-. As NaOH is added, the OH- ions will react with the HA, causing it to deprotonate and shift the equilibrium towards the A- form. This will lead to a gradual increase in pH as the weak acid is neutralized. Beyond the equivalence point, the excess OH- ions will continue to react with the A- ions, resulting in a slower rise in the pH compared to the HCl titration curve.
In summary, HCl titration curve will show a rapid drop in pH followed by a steep rise after the equivalence point, while the weak acid HA titration curve will exhibit a gradual increase in pH throughout the titration, including beyond the equivalence point.
To compare the titration curves of these two experiments at 10 or 15 mL of NaOH beyond the equivalence point, we need to understand the chemical reactions occurring and the principles of acid-base titration.
In both experiments, the NaOH is being titrated into the acidic solutions, resulting in a neutralization reaction. The reaction between HCl and NaOH is a strong acid-strong base neutralization, while the reaction between the unknown weak acid HA and NaOH is a weak acid-strong base neutralization.
During the titration process, the pH of the solution changes as the base (NaOH) is added. The pH can be measured using an indicator or a pH electrode, and this information can be used to construct a titration curve.
At the equivalence point, the moles of acid are stoichiometrically equivalent to the moles of base. For a strong acid-strong base titration, the equivalence point occurs at a pH of 7, indicating a neutral solution.
For a weak acid-strong base titration, the equivalence point occurs at a higher pH value than 7 because the weak acid does not fully dissociate in water. The pH at the equivalence point will depend on the strength of the weak acid and its initial concentration.
Now, considering the comparison of the two titration curves at 10 or 15 mL of NaOH beyond the equivalence point, we can expect the following:
1. For the HCl-NaOH titration curve: Since HCl is a strong acid and NaOH a strong base, the reaction proceeds to completion at the equivalence point, resulting in a sharp change in pH. Beyond the equivalence point, the pH will increase rapidly, indicating an excess of base.
2. For the HA-NaOH titration curve: Since HA is a weak acid, the pH at the equivalence point will be greater than 7. Beyond the equivalence point, the excess of NaOH will continue to react with HA, driving pH even higher.
In summary, both titration curves will show an initial increase in pH up to the equivalence point. However, the HCl-NaOH titration curve will sharply decrease pH beyond the equivalence point, while the HA-NaOH titration curve will continue to increase pH.
The key difference is due to the nature of acids being titrated: HCl is a strong acid, and HA is a weak acid. This difference leads to variations in the pH change during and after the titration process.
0.500\40=0.0125
0.0125\0.025=0.5