Calculate the pH of a buffer that is 0.13 M in lactic acid and 0.11 M in sodium lactate
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Complete Question:
Consider these three titrations: (i) the titration of 25.0 mL of a 0.100 M monoprotic weak acid with 0.100 M NaOH (ii) the titration of 25.0 mL of a 0.100 M diprotic weak acid with 0.100 M NaOH (iii) the titration of 25.0 mL of a 0.100 M strong acid with 0.100 M NaOH. Which statement is most likely to be true?
(a) All three titrations require the same volume of NaOH to reach their first equivalence point.
(b) All three titrations have the same initial pH.
(c) All three titrations have the same pH at their first equivalence point.
Answer:
(a) All three titrations require the same volume of NaOH to reach their first equivalence point.
Explanation:
(i) the titration of 25.0 mL of a 0.100 M monoprotic weak acid with 0.100 M NaOH
number of moles of acid = = 0.0025 moles
ii) the titration of 25.0 mL of a 0.100 M diprotic weak acid with 0.100 M NaOH
number of moles of acid = = 0.0025 moles
(iii) the titration of 25.0 mL of a 0.100 M strong acid with 0.100 M NaOH
number of moles of acid = = 0.0025 moles
Therefore, all the acids require the same number of moles of NaOH to reach their first equivalence points
Note that the concentration of the base NaOH are also the same, therefore the volume of NaOH required to reach equivalence point would also be the same for all the three titrations.
All three titrations don't have the same initial and equivalence point pH because they all have different acidic properties.