Studying the pH of Strong Acid,Weak Acid, Salt and Buffer solutions
The objective of this experiment was to compare calculated and measured pHs of acidic solutions. Using the pH the acid dissociation constant of acetic acid could be determined
We preformed experiment in part III which was preparing HC2H3O2 solutions and determining pH.
5 ML OF 0.10M HC2H3O2 in a clean dry 5ml were collected in a graduated cylinder. 4 test tubes were placed on a test tube rack and in the first tube 2.5 ml of HC2H3O2 was transferred. The remaing of the coultion was ttransfered to a clean beaker while the graduated cylinder was rinsed and the rinses were added to the new beaker. The solution was mixed thoroughly after being mixed with 25ml of distilled water. 2. 5ml of that solution was poured into the second test tube. 2.5 ml of that wasm solution was poured onto a second graduated cylinder . add 20 ml of rinses from the first 50 ml beaker to the discared solutions beaker. Dilute the second solution with 25ml of distilled water and add 2.5 of this solution to test tube 3. Repeat this process for test tube 4.
To measure the pH we transferred the solutios in the test tubes into separate labeled beakers and insterted the pH Meter. Rinsing the electrode with distilled water each time.
Data and Calculations
From our calculations it can be seen that as the concentration of HC2H3O2 decreased, the pH of our solution increased. Meaning it became more basic.
Weak acids are acids that 10% or less of their molecules dissociate in water. In weak acids the [H3O+] is lower than the concentration of the acid that was introduced. The Ka for HC2H3O2 is 1.8x10-5 which is kinda small so we can do approximation for the pH even though using the quadratic equation would be better.
The weak acid which was the one we worked with HC2H3O2 had different pHs even though their concentraions were the same. That just goes to show that strong...