If you have 0.100 M Pyridine titrated with 0.100 M HCl, choose an appropriate indicator and explain?
Pyridine we will call Py
When we titrate this base, the equivalence point will occur when only the salt is present. It will hydrolyze. You can calculate the pH at that point.
PyH^+ + H2O ==> H3O^+ + Py
Ka for PyH^+ = (Kw/Kb) where Kw is 1 x 10^-14 and Kb is the ionization constant for pyridine. Set up an ICE chart, substitute into the Ka expression and solve for OH^-, then convert to pOH and finally to pH. The concn of the salt will be 0.05. I found the pH to be approximately 3.2 so you would want an indicator that would change at that point; i.e., 3.2 would be the middle of the range for the indicator.
To choose an appropriate indicator for the titration of 0.100 M Pyridine with 0.100 M HCl, we need to consider the pH range at which the color change of the indicator occurs.
In this case, Pyridine is a weak base and HCl is a strong acid. The reaction between Pyridine and HCl can be represented as follows:
Pyridine + HCl -> Pyridinium Chloride
The pH range at which this reaction occurs is generally around pH 4 to 6.
To choose an appropriate indicator, we want one that changes color within this pH range. One commonly used indicator for acid-base titrations within this pH range is Methyl Orange.
Methyl Orange has a pH range of approximately 3 to 4.4. It is yellow in a basic solution and changes to red at low pH values. Since the expected pH range for the reaction between Pyridine and HCl falls within the pH range of Methyl Orange, it would be a suitable indicator for this titration.
It's important to note that the specific choice of indicator may vary depending on the desired accuracy, the expected pH range of the titration, and the concentration of the substances involved. Always consult the literature or a chemistry reference for the most appropriate indicator based on the specific experimental conditions.