Titrations of Polyprotic Acids

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Күн бұрын

Similarity to monoprotic acid titrations. “Chunking” into multiple titrations. Species and equilibria in buffer regions. Identifying pKa1 and pKa2.
00:00 Introduction
00:51 The "First" Titration
03:17 The "Second" Titration

Пікірлер: 28

@robingall4400 4 жыл бұрын

I have a PhD in chemistry but haven't done acid base chemistry in years but needed to help my daughter who is home from college during pandemic and this was an awesome refresher!

@FreedVoid 5 жыл бұрын

To the point and well-explained :). Thank you very much!

@spencersteinmetz2994 7 жыл бұрын

Great explanation, it really helped sort this out for me!

@pseudomonas69 6 жыл бұрын

thank you Michael Evans :,)

@lasanniranjithwimalasuriya2242 7 жыл бұрын

Thank you. It really helped. I have my A2 exams in a few hours and this was the area i wasnt quite confident about. Great explanation

@mevansthechemist 7 жыл бұрын

Thanks! Hope your exams went well!

@lasanniranjithwimalasuriya2242 7 жыл бұрын

Michael Evans it did we got a question on the buffer region you explained where pKa=pH

@debanganamoitra114 3 жыл бұрын

Thank you so much. You have cleared my doubt on finding the pka2 from the titration curve, since I could not understand why the pH at half of neutralization point was not coming as pka2

@dgmoon28 6 жыл бұрын

thank u so much 🙌💕💕💕💕baghdad

@hivirupalihena3102 Жыл бұрын

Thank you so much, This is the explanation realy I needed

@xianhuang4535 4 жыл бұрын

Thank you! It's bery useful. But just wondering a point: why there is a steep increase at the first equivalence point? Should those two buffer regions connected together? Because there is no sudden increase in [H+] at the first equivalence point. I will quite appreaciate if anyone can answer me this question.

@pandugus1550 6 жыл бұрын

How about diprotic weak base titration with strong acid (e.g Quinine, Piperazine)

@readytolearn77 Жыл бұрын

Thank you

@opiumx1993 6 жыл бұрын

Hi, how to calculate acid concentration from this titration?

@pink_floyd1 5 жыл бұрын

what do you mean

@pink_floyd1 5 жыл бұрын

[CoVo(for acid)-V(aded)C(NaOH)]/Vo+V(aded) . for one protonic acids

@angelosperperis7961 3 жыл бұрын

At 3:24 shouldn't the point where [H2A] is practically zero be at the middle of the 1st steep section?

@mevansthechemist 3 жыл бұрын

Good point-it can also be said of the first equivalence point that [H2A] is essentially zero there. Of course, where it's indicated at 3:24 in the central flat region of the curve, [H2A] is even smaller! It is important to keep in mind that at the equivalence point, some back reaction of HA- with water produces H2A and hydroxide.

@doodle_kudul 6 жыл бұрын

Very nice explanation. Can you help me getting pH at both the equivalent points??

@mevansthechemist 6 жыл бұрын

Arup, the key is to realize that at each equivalence point, all you have is a solution of the conjugate (acid/base) of whatever you started with. (Here, we have a solution of the conjugate bases at each equivalence point.) The volume at this point is the sum of the volume of titrant added and the volume of analyte solution. To calculate the pH, treat the solution as a weak acid/base solution (as the case may be).

@doodle_kudul 6 жыл бұрын

Michael Evans thanks a lot.

@RatuAdellya 7 жыл бұрын

how to calculate the pH at equivalence point:(

@spencersteinmetz2994 7 жыл бұрын

Use an ice table

@MY-hc5fb 6 жыл бұрын

Since all you have is your conjugate base of your acid, it'll be that reacting with water. You then make an ice table and get Kb = x^2/(conc of base -x), the x in the denominator we can usually ignore because Kb is usually very small. Since you only know the Ka of your acid, you will use this equation KaKb = Kw and solve for Kb. The x in the above equation is equal to the OH- concentration. Then you use your OH- concentration, calculate the pOH and use that to get your pH. (Sorry this is late.)

@pink_floyd1 5 жыл бұрын

from hydrolize reacion

@afnandabobash5468 5 жыл бұрын

At 3.24 minute there is some thing maybe wrong 🙈🌿 when you divide (A-/HA) TO Prove PH=PKa1 from handerson equation?? Thank you very much 🍂🌺

@rbmarik6082 4 жыл бұрын

yeah I felt the same!

@mevansthechemist 4 жыл бұрын

Oy, that should have read [HA-]/[H2A] inside the parentheses. Right idea, but the wrong molecules were written inside the brackets. Good catch, and thanks!