I had to calculate the conjugate base/acid ratio of phenol red in a phenol red solution prepared with a buffer I made and the base/acid ratio of just the phosphate buffer I made. I need to understand why these ratios are different. Can anyone help?
I suggest you write the two structures for each system as the acid + OH^- ==> conj base, plug in the concns from your data and you can see how/why the ratio is different.
Yes, I can help you understand why the conjugate base/acid ratio of phenol red in a phenol red solution prepared with a buffer and the base/acid ratio of just the phosphate buffer are different.
To understand this, let's start by discussing what a buffer is. A buffer is a solution that helps maintain a relatively constant pH when there are changes in the amount of acid or base added to it. Buffers consist of a weak acid and its conjugate base (or a weak base and its conjugate acid).
Phenol red is a pH indicator that changes color depending on the pH of the solution. It acts as both a weak acid and its conjugate base. In an acidic solution, it exists mostly as a protonated form which is the weak acid, and in a basic solution, it exists mostly as a deprotonated form which is the conjugate base.
When you prepare a phenol red solution using a buffer you made, the buffer will have its own weak acid and conjugate base. The pH of the solution will depend on the relative concentrations of the weak acid and conjugate base of the buffer, as well as the equilibrium between the weak acid form and the conjugate base form of phenol red.
The conjugate base/acid ratio in the phenol red solution will be determined by the equilibrium constant (Ka) of phenol red, as well as the pH of the solution. The Ka is a measure of the strength of the weak acid and its conjugate base.
On the other hand, when you calculate the base/acid ratio of just the phosphate buffer you made, it will depend solely on the relative concentrations of the weak acid and its conjugate base in the buffer. This ratio will not take into account the equilibrium with phenol red.
Therefore, the conjugate base/acid ratio of phenol red in the phenol red solution prepared with the buffer may differ from the base/acid ratio of just the phosphate buffer because the phenol red solution is influenced by both the equilibrium between weak acid and its conjugate base in the buffer as well as the equilibrium of phenol red itself.
In summary, the conjugate base/acid ratio of phenol red in the phenol red solution is influenced by both the equilibrium of phenol red and the equilibrium of the weak acid and conjugate base in the buffer. On the other hand, the base/acid ratio of just the phosphate buffer only considers the equilibrium of the weak acid and its conjugate base in the buffer.