Acid Dissociation Constant Puns

I'm writing a paper about determining the pKa of an amino acid using a pH sensor. In one of the investigations, a weak acid is dissolved in HCL and titrated with NaOH. I found the pKa using the first and second derivatives of the pH vs volume graphs. But is there a way to determine it theoretically (as in by calculation)? I have attempted to find a theoretical measure for the pKa but my instructor told me it's irrelevant as it only considers the dissociation of the weak acid or only the dissociation of HCL. My question is: is it possible if both NaOH and HCL concentrations are known?

I'm not asking for a full solution, I just need someone to tell me if it's doable and put me in the right direction.

Thanks!

Butyric acid C₃H₇COOH is a weak acid.

a) Write the formula for the equilibrium that is established when butyric acid is dissolved in water.

b) Draw the expression for the acid dissociation constant, Ka (including unit).

Here's the answer for the question:

>a) C₃H₇COOH(aq) + H₂O(l) ⇄C₃H₇COO⁻ (aq) + H₃O⁺ (aq)
>
>E-level: Charges on the ions are missing.
>
>C level: Correct.
>
>b) E-level: Ka = ([C₃H₇COO⁻] · [H₃O⁺]/[C₃H₇COOH]) mol/dm³

So, why was H₂O included in the chemical reaction. In my textbook, it said that ... in a dilute aqueous solution of an acid, the water concentration is so high that it can be considered unaffected by the reaction with the acid (the water concentration can be considered to remain as large as in pure water, i.e. constant).

What's the rule of thumb for when we should include H₂O in a chemical reaction? It says in the question that the ”butyric acid is dissolved in water.”

In b), they seem to have omitted the H₂O in the expression for the acid dissociation constant? So like, can someone explain? I'm new to this area.

I was given the following Question

https://preview.redd.it/veeqtxjw29331.png?width=1282&format=png&auto=webp&s=b104289c603e081534ff218574d55209d681493b

Here is my working:
The top equation results in an answer of 2.29
The bottom equation results in an answer of 9.19 (shown on calulator)

https://preview.redd.it/k55rgqt039331.png?width=578&format=png&auto=webp&s=f07fded0778b2d63eb064bdc61356854128817f8

I asked my teacher why this was wrong and she said that it Ka wasn't calculated with Moles/Litre but rather Moles/volume of container.

This didn't make sense to me as it would mean that every time you pour solution into a container the Ka value would change. (unless it does???)

I also thought that when written [molecule] that meant Moles per litre of that molecule.

This question goes towards everyone's university grades.

Can someone clarify this for me?
Thankyou :)

Can someone help me find the answer ?

0.554 mol of a weak acid, HA, and 13.2 g of NaOH are placed in enough water to produce 1.00 L of solution. The final pH of this solution is 4.11. Calculate the ionization constant, Ka, of HA.

I am not sure if in this situation I must find the limitant reactant , and if so what to do next ?

http://imgur.com/a/dOKr3

I'm on a time deadline, I was hoping somebody could take a look and I'd come back later and post my work

Thanks in advance

I understand pKa values in water in terms of determining which molecules will deprotonate which other molecules, but for extreme values, I can't wrap my head around the definition.

For example, methane has a pKa of ~50. Does this really mean that the ratio [CH3-] [H+] / [CH4] in water is 10^-50 ? This would mean something like one dissociation if the whole mass of the Earth in methane was in contact with water. It doesn't seem sensible.

I read that extreme values are not found by titration, but by NMR or other techniques. So does this scale really have anything to do with dissociation in water above 12 or below 2, or is it just an extension that effectively drops the original definition?

I also read, on the wikipedia article for example, that NaOH has a pKa of around 13 or 13.7. I really don't understand this at all, is this correct? Is the ratio of [NaO-] [H+] / [NaOH] really 10^-13 ? I thought that it would be completely dissociated as Na+ and OH- so I cannot really make sense of this. Do I interpret it as NaOH donating a proton slightly more easily than H2O, even though I can't think of a situation where it would do that?

Thanks!

Hi there,

I am specifically looking to find the pKa of methyl red. Wikipedia and countless other sources are failing me, because they only list the value up to 1 decimal point. It is usually listed either as 5.0 or 5.1.

After a lab, I determined the value to be 5.06, but I want a precise value from some kind of available literature to be able to compare to in my report.

Can somebody help me out? Thank you!

Idk if the term 'dissociation' fits here, but I've been feeling so detached from real life and myself. Most of the time I go through the day like on "3rd person's mode" in a video game. I'm constantly aware of how I look/may look, even when I'm home alone. When I'm doing something, instead of focusing, I wonder how I look doing it. Combined with my depression and anxiety, this constant worry takes all the pleasure from life. I can't even sit down and fully enjoy a movie without thinking about how I look. I'm so tired of this constant stress.

I need help. I'm in a dissociative state most of the time (like 60-70%) it has been like that for at least a month. The thing is that it's not too intense, actually it's pretty mild, but it's extremely hard to get out of it.

Grounding doesn't work, sometimes the more I try to focus on reality through my senses the more unfamiliar it feels and I disconnect even more from it.

My memory is broken. When I remember something that happened the day before or the current day I feel it was ages ago or didn't even happen.

Is my brain broken? Is there any way to fix this? Could it be another disorder? I just need something that makes it stop because I can't stand it.

I feel very isolated from "real life" everything feels very distant and most of the time it barely feels real to me.

I feel like I am constantly waiting. Like life is a game and I am in the tutorial section waiting for the real game to start. and I keep telling myself alright its about to happen. its about to happen.

but the truth is life is already happening and keeps happening. but now I feel like life is moving forward and I am left out. like I fell through some loop hole. I am stuck in this vacuum of space. forced to remain frozen without moving. I am terrified that one day I am going to "wake up" and find that everyone in this race of life is already at the finish line. everyone is successful and "living"

i cant describe it but I don't feel like I am living at all. I feel isolated and I feel like there is a glass barrier between me and real life. and I just cant get passed it. I also cant bring myself to care? the feeling that I am not living and this feeling of panic and urgency is diluted and far away.

my life is getting wasted away and I am not doing anything in my days just avoiding having to live.

I personally have never experienced dissociation, I don't know how to help them when it happens. I will give them kind words and stay with them but I'm not sure whether its enough to help.

Hi guys, first time posting here. I hope you can help me with this.

I have been in a constant state of dissociation since 11 (it's 19:00 as I am typing this) and I don't know how to get rid of it. It's so overwhelming. Do you know coping mechanisms that work for you?

I started having panic attacks almost 4 months ago but I havent had one in so long (more than 3 mobths). However, what was left was despersonalization, mildly for the most part, but since monday Ive been struggling with it and today has been by far my worst day.

Any experience, advice and/or help would be much appreciated.

My first experience with dissociation began when I was around 10 years old when my dad died; I also was experiencing severe anxiety and frequent panic attacks. I finally got on lexapro 10mg to help with my depression and anxiety and as a result, my dissociation went away. The lexapro worked FABULOUSLY for 10 years and then suddenly one day it appeared that it wasn’t as effective as it had been. My disassociation came back as well as depression and anxiety symptoms. I had my lexapro increased to 20mg. Unfortunately there was no change. I felt the same. I finally worked up the courage to see another psychiatrist after 10 years and got switched to Zoloft 50mg, in hopes that it would ease my dissociation. After awaiting a long 4-6 weeks, I felt no difference. If anything, I just feel slightly more anxious. This constant dissociation is effecting my life. I dropped out of school and significantly pulled my hours back at work. It’s been almost over a year since I felt “alive”.

I feel like I'm in a constant mild dissociation and because of this I cant enjoy life I cant physically process or learn things sometimes because my too much of my brain is being used to process or fight/block my trauma. And I also feel like I dont realize what is really going on around me...for example I thought my life was super empty but looking back now I realize I got to do alot of cool stuff j just didnt realize because I was mildly partly dissociated during these cool things. I feel like cuz of this my life is passing me by and I dont even realize because my brain has locked me in some confused dazed state where I dont fully 100% understand or see what Is going on. I'm there physically but I'm not there really ...I feel like espally in childhood I was always in a shut down freeze mode even at school for no reason other than I learned that to be safe state. You cant get anything done in that state you cant do anything in that state expect watch as things happen to you or around you, and unforantley that was my eveeyday normal state to be in since my parents were violent and abusive many times a day almost everyday. My dissociation is very mild and I can still function at a basic level so I wonder if this is truely dissociation but a few people outside my family point out how I'm always spacing out and not "there".

Well at least I think?

I don't really know what normal is. ig its just not feeling out of it.

But isn't that me just not focusing on the dissociation?

Even when I don't feel anxious or uncomfortable everything still feels a bit trippy and weird, maybe I'm just crazy who the fuck knows

Ive been doing all the healthy things I can (when I can be bothered) and I'm getting better at controlling this stuff but I can't really say I feel normal

Because even when im not anxious I still feel numb to my surroundings and have the whole cant focus, well I can but not really present type thing kinda hard to explain it

I think im going to be like this forever and that's not said with anxiety thats just said with what I believe I don't think im getting connection back but I guess I can get some kind of normal stability back?

Basically I just don't understand even though I think im not dissociating hard i still feel numb

if anyone who has suffered from constant dissociation in the past and has began the recovery process, please share your story, thanks!

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i find myself getting triggered whenever i’m not doing anything. my mind goes into these thoughts of trauma. if my mind is occupied completely, i actually have a sense of fun and meaning. how would i go about addressing the triggers? thanks

https://preview.redd.it/go2cd2lyynf71.png?width=2732&format=png&auto=webp&s=5215db013afb3199c4eb26b0521be2d263e59ef9

I’m 22f who is basically dissociated at all points in my life. I’ve talked to some counsellors about it and they suggested grounding techniques and mindfulness and all that kind of stuff but they make me worse.

I’m mostly passively dissociated but when I ground myself or make myself more aware of the world around me, it just makes me hyper aware of everything not being right.

The feeling I get is the same feeling I imagine VR feels like. I’m looking at this world and there’s nothing in my view that’s particularly suspicious, but I know it’s not real.

When I see myself in the mirror, it’s not me. When I look at those close to me, I find it hard to connect to them in any way because I don’t feel anything about them.

I guess I’m making this post because I’ve suffered with dissociation, DR and DP for a long time but the last two years have been hell because I’m never not dissociated. Have you got any advice? Any success stories? I don’t know, I think I’m just fed up of not living.

I mean you can’t leave the house, work , school , socialize etc...

If HA is a weak acid with acid-dissociation constant Ka, added to water so that its initial concentration is c, the following ICE tables can be constructed.

Then, we have

https://preview.redd.it/nqqke00np3k71.png?width=1058&format=png&auto=webp&s=f1b92347b03865b1e99a0f8d9c915277bd10407c

How do we simplify this cubic to obtain the usual result that x = sqrt(cKa), or something better that is more easily solvable than a cubic? Is it correct to say that x is small for larger concentrations and ignore the x^3 term to get a quadratic?

I'm writing a paper about determining the pKa of an amino acid using a pH sensor. In one of the investigations, a weak acid is dissolved in HCL and titrated with NaOH. I found the pKa using the first and second derivatives of the pH vs volume graphs. But is there a way to determine it theoretically (as in by calculation)? I have attempted to find a theoretical measure for the pKa but my instructor told me it's irrelevant as it only considers the dissociation of the weak acid or only the dissociation of HCL. My question is: is it possible given both NaOH and HCL concentrations are known?

I'm not asking for a full solution, I just need someone to tell me if it's doable and put me in the right direction.

Thanks!

Butyric acid C₃H₇COOH is a weak acid.

a) Write the formula for the equilibrium that is established when butyric acid is dissolved in water.

b) Draw the expression for the acid dissociation constant, Ka (including unit).

Here's the answer for the question:

>a) C₃H₇COOH(aq) + H₂O(l) ⇄C₃H₇COO⁻ (aq) + H₃O⁺ (aq)
E-level: Charges on the ions are missing.
C level: Correct.
b) E-level: Ka = ([C₃H₇COO⁻] · [H₃O⁺]/[C₃H₇COOH]) mol/dm³

So, why was H₂O included in the chemical reaction. In my textbook, it said that ... in a dilute aqueous solution of an acid, the water concentration is so high that it can be considered unaffected by the reaction with the acid (the water concentration can be considered to remain as large as in pure water, i.e. constant).

What's the rule of thumb for when we should include H₂O in a chemical reaction? It says in the question that the ”butyric acid is dissolved in water.”

In b), they seem to have omitted the H₂O in the expression for the acid dissociation constant? So like, can someone explain? I'm new to this area.

Or can both be true?