Question

Include a brief (fewer than 4 sentence) explanation for each of the following that cites raw data or information gathered from plots:

a. Compare the addition of a strong acid to water and the addition of a strong acid to your buffer. Suggest a reason for any difference you observe.

b. Describe the effect of diluting a buffer. What happens when you dilute an acid? Upon sufficient dilution, what would you predict the final pH to be on the pH scale (1 to 14)?

c. In both words and in terms of a mathematical equation, describe the relationship between pH and the ratio of conjugate base to acid concentration that you observed in this experiment. Compare the plots of [conj. base]/[conj. acid] vs. pH and log([conj. base]/[conj. acid]) vs. pH

Answer 1

a. Compare the addition of a strong acid to water and the addition of a strong acid to your buffer. Suggest a reason for any difference you observe.

addition of storng acid to water --> extremely large drop in pH, i.e. from pH = 7, to about 1-2 depending in concentration

For strong acid + buffer --> small pH change, since buffer will actualy shift euqilibriums in order to lower the impact of H+ addition

b. Describe the effect of diluting a buffer. What happens when you dilute an acid? Upon sufficient dilution, what would you predict the final pH to be on the pH scale (1 to 14)?

If we dilute the buffer, we remain with the pH, but eventually you will start losing pH power

when the buffer is so dilute, the the pH tends to 7, since [H+] from water = 10^-7

c. In both words and in terms of a mathematical equation, describe the relationship between pH and the ratio of conjugate base to acid concentration that you observed in this experiment. Compare the plots of [conj. base]/[conj. acid] vs. pH and log([conj. base]/[conj. acid]) vs. pH

in math:

pH = pKa + log(conj. base / acid)

clearly, as wee add more acid, the log decreases so the pH decrases, i.e. more acidic as expected

clearly, as wee add more base , the log increases so the pH increases , i.e. more basic as expected