The purpose should include a majority of the topics and techniques covered in the experiment. The procedure section should cite the lab manual and include any changes made to the procedure during lab work. It should also include the buffer and pH used, and the amount of acid and base weighed out. The data section should include tables with the following: The concentration of acid and conjugate base after each addition of HCl or NaOH and the resulting pH for a) your buffer, b) diluted buffer and c) distilled water. This can be done by using the Henderson-Hasselbalch equation. The Henderson Hasselbalch equation can be used in the following manner when solving for the concentration of acid after an addition. You know the pH, the pKa (it was given to you in the pre-lab) and the concentration of acid and base in your buffer solution. Make sure you calculate this according to the amounts you weighed out in lab and the actual volume used. Plug everything you know into the above equation and solve for the x, which will be the concentration of acid and base after HCl was added. Finally subtract x from the amount of base in your buffer solution and add x to the amount of acid in your solution. This is because you are adding acid to your buffer solution and in order for it to stay a buffer you must account for the equilibrium shift that occurs from the base to the acid. These steps will give you the new concentration of acid and base at the new pH if HCl is added. If NaOH is added you will follow the same steps but use this variation of the Henderson Hasselbalch equation.
NOTE: The concentration of acid in the buffer and diluted buffer is not the same. Also for the water system look up the pKa value of water and the concentration of acid and base in water.
A sample calculation of how to prepare the buffer solution at the assigned pH and a sample calculation for determining the acid and base concentration after the addition of HCl or NaOH should be included. The conclusion section should include several paragraphs with the following: A summary statement of buffer and pH used, a discussion on the similarities and differences between the buffer and dilute buffer, a summary of trends in the data, a discussion of the results of the distilled water and dilute buffer and any possible errors. Answer the following question:
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Hydrogen Phosphate Buffer Systems
