Santa Monica College Generic Reaction for Questions Lab Repoort

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znegvarm123

Science

Santa Monica College

Description

Buffer solutions 

https://openstax.org/books/chemistry-2e/pages/h-io...

https://youtu.be/kBzPTEB21Po

https://youtu.be/PD0ycVlGtTQ

https://youtu.be/XcSZ5jeG5mA

https://youtu.be/tvCyrBHJfBk

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Explanation & Answer

View attached explanation and answer. Let me know if you have any questions.Hello! Here are the answers to the questions. ^^
View attached explanation and answer. Let me know if you have any questions.Sure! Here it is.

Consider this generic reaction for questions #1 & #2.: HA + OH- ⇌ A- + H2O
1) As acid (H+) is added to the buffer solution, what species reacts with H+ that keeps the
pH from changing significantly?
The acid that is added to the buffer solution will react with the conjugate base A- to form
the weak acid HA. This will significantly counter the supposed decrease in pH that is
associated with the addition of the acid.
2) As base (OH-) is added to the buffer solution, what species reacts with OH- that keeps
the pH from changing significantly?
The base that is added to the buffer solution will react with the weak acid HA to form the
conjugate base A-. The weak acid will give up its H+ to counter the addition of the base and
form water. This will counter the supposed increase in pH that is associated with the
addition of the base.
3) What species in the blood maintains the pH at ~7.4?
The pH of blood is maintained by the carbonic acid (H2CO3) – bicarbonate (HCO3-)
buffering system.
4) Define equivalence point.
The equivalence point is the point in the titration process where the added amount of
titrant is exactly enough to neutralize all of the analyte. In an acid-base titration, it is when
the moles of the acid and the base in the analyte solution is equal.
5) Define half-equivalence point.
Just like what its name suggests, the half-equivalence point is the point in the titration
process where the added amount of titrant is exactly enough to neutralize half of the
analyte. In an acid-base titration where the base is the titrant, it is when the moles of the
base added is half the moles of the acid in the analyte solution. An important implication of
this is that the conjugate pairs involved will have the same concentration.
6) Is the middle of the buffer region the half-equivalence point?
Yes. The middle of the buffer region is the same as the half-equivalence point where the
added amount of titrant is exactly enough to neutralize half of the analyte, and there is
equal concentrations of the conjugate pair species.

7) Suppose the pH at the equivalence point = 8.72, and the pH at the half-equivalence point
= 4.61, what is the pKa of the acid?
Looking back at the implication mentioned at the half-equivalence point, the conjugate
pairs involved will have the same concentration at this point. When this is plugged into the
Henderson-Hasselbach equation, what’s left is pH=pKa. Therefore, the pH at the halfequivalence point is the pKa of the acid.
8) Suppose the pH at the half-equivalence point = 5.63, what is the Ka of the acid? [SHOW
WORK]
The pH at the half-equivale...


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Just what I needed…Fantastic!

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