assume all of the ionized aspirin remains in the buffer solution and all of the un-ionized aspirin goes into to the ethyl acetate, what is the molarity of the aspirin in the ethyl acetate at pH 2 and pH 8? what equation would ou use for this?
To calculate the molarity of aspirin in ethyl acetate at different pH values, we need to consider the ionization equilibrium of aspirin in water. Aspirin (acetylsalicylic acid) exists in both ionized and un-ionized forms in an aqueous solution.
The ionization equilibrium of aspirin can be represented by the following reaction:
Aspirin (HAc) ⇌ Acetate ion (Ac-) + Hydrogen ion (H+)
The equilibrium constant for this reaction is known as the acid dissociation constant (Ka) and can be expressed as:
Ka = [Ac-][H+]/[HAc]
Now, let's consider the pH values of 2 and 8 separately.
1. pH = 2:
At this pH, the concentration of hydrogen ions (H+) is higher, favoring the ionization of aspirin. Therefore, a larger portion of aspirin will be ionized in the ethyl acetate layer.
To calculate the molarity of aspirin in ethyl acetate at pH 2, you would need to know the initial molarity of aspirin in the buffer solution and the partition coefficient between water and ethyl acetate. The partition coefficient (K) represents the ratio of the concentration of a solute in one solvent (ethyl acetate) to its concentration in another solvent (water).
Molarity of aspirin in ethyl acetate at pH 2 = Molarity of un-ionized aspirin at pH 2 × K
2. pH = 8:
At this pH, the concentration of hydrogen ions (H+) is lower, favoring the un-ionized form of aspirin. Therefore, a larger portion of aspirin will be in the un-ionized form in the ethyl acetate layer.
To calculate the molarity of aspirin in ethyl acetate at pH 8, you would once again need the initial molarity of aspirin in the buffer solution and the partition coefficient between water and ethyl acetate.
Molarity of aspirin in ethyl acetate at pH 8 = Molarity of ionized aspirin at pH 8 × K
In both cases, the partition coefficient (K) should be determined experimentally or obtained from reliable sources for the specific system under study.
To summarize, the equation(s) you would use to calculate the molarity of aspirin in ethyl acetate at a specific pH involve the use of the initial molarity of aspirin in the buffer solution, the partition coefficient between water and ethyl acetate, and the extent of ionization of aspirin determined by the pH of the solution.