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Buffers and Salts Lab

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Submitted By visiongurl5
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Post-Lab Questions
a. The relationship of the pH to the ratio of concentrations of the conjugate base to conjugate acid is based on the Henderson Hasselbalch equation, pH=pKA+ log([conjugate base] / [conjugate acid]). The graph of the relationship between pH and this ratio showed to increase rapidly at first, and then more slowly. This shows a logarithmic curve and that the relationship of the ratio is a logarithmic function of pH. When pH was graphed with the log of this ratio, the graph became linear, showing the directly proportional relationship between pH and the log of the ratio of conjugate base to conjugate acid. This proves the Henderson Hasselbalch equation.

b. The addition of a strong acid would decrease the pH, since water is a neutral solution. It has nothing to account for the increase of H+ ions. The addition of a strong acid to the buffer, however, would generally not affect the pH. The buffer has a conjugate base which would be able to accept the excess of H+ ions, therefore not greatly effecting the pH. H3O+ would form, which would then react with A- to form HA and H2O.

c. Diluting the acid would overall increase the pH of the solution. The dilution would cause an increase in volume, while the moles of H+ ions remains the same, therefore decreasing the concentration of H+ ions. If sufficiently diluted, the solution would become neutral with a pH of 7.

d. The pH value of our most diluted buffer sample compared to our undiluted sample were not as similar as we would have expected. We believe that the difference in pH’s is due to the minimal time allowed for the undiluted buffer to reach equilibrium before having the pH measured. In addition to this, our pH meter was malfunctioning and had to be zero’d several times throughout the lab. The difference between the first and second dilutions was more appropriate for a buffer, showing…...

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