The Periodic Table

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CowperKettle

04:53

> Sir James Dewar
Is a better man than you are
None of you asses
Can liquefy gases.

A clerihew () is a whimsical, four-line biographical poem invented by Edmund Clerihew Bentley. The first line is the name of the poem's subject, usually a famous person put in an absurd light, or revealing something unknown or spurious about them. The rhyme scheme is AABB, and the rhymes are often forced. The line length and metre are irregular. Bentley invented the clerihew in school and then popularized it in books. One of his best known is this (1905): == Form == A clerihew has the following properties: It is biographical and usually whimsical, showing the subject from an unusual point of...

Hot nitric acid (HNQ)

05:20

Q: On the spin-adaptation of 2nd order Møller-Plesset perturbation theory

$\newcommand{\Ket}[1]{\left|#1\right>}$ $\newcommand{\Bra}[1]{\left<#1\right|}$ $\newcommand{\BraKet}[2] { {\left<#1} \left|#2 \right>}$ In spin adaptation (common in electronic structure theory) we approximate that the spin-up and spin-down spin orbitals (herein assumed to be real and represente...

11 hours later…

Hot nitric acid (HNQ)

16:11

Q: What does an electron's spin of 0.5 and minus 0.5 signify?

While teaching me magnetism, my teacher told me about the spin of an electron. He told me that the spin of .5 means that if we rotate the electron twice counter-clockwise on its axis, we would have the same face(picture) of the electron. And if we rotate an electron of -0.5 spin twice in the oppo...

quantum-chemistry electrons spin

1 hour later…

Anindya Prithvi

17:40

@orthocresol , @FadedGiant need help in merging question with my acc, raised a flag, non responsive

Hot nitric acid (HNQ)

17:52

Q: Why is borole not considered aromatic

I came across a problem which stated that borole isn't aromatic. I thought that borole is similar to pyrrole so it should be aromatic, but that isn't the case. Can I know why isn't it aromatic? I was also wondering if we replace the nitrogen in pyridine with boron then will the compound remain ar...

organic-chemistry aromaticity

anongoodnurse

18:02

Is this the site's chat room? Never tried to find Chemistry's chat.

M.A.R.

@anongoodnurse Hello, and welcome!

anongoodnurse

Oh, thank you. I'm so embarassed, but I need some very. basic. help.

M.A.R.

Sure, if I can be of any help

anongoodnurse

while I loved Biochemistry, and tolerated Organic Chem, I absolutely hated chemistry. pKa, mM, etc. make me anxious.

M.A.R.

Writes equations involving lots of pK's

Anindya Prithvi

18:05

Are there mods on chem se

M.A.R.

@AnindyaPrithvi No it's mostly just a picnic

anongoodnurse

@M.A.R. lol! I need to figure out (please don't laugh) how much citric acid (in grams) in, say, a liter of water will give me a pH of 3.2

I tried, I honestly did.

M.A.R.

@anongoodnurse Ha, OK, polyprotic, a bit of a mess, lemme think

anongoodnurse

I got the molecular weight, the pKa, all that stuff...

not to mention there are different values for pKa...

three H+ ions?

M.A.R.

Yes, three acidic hydrogens from carboxylic acids that can protonate water

Very weakly. How accurate does the result need to be?

anongoodnurse

18:08

@M.A.R. yeah, so I learned, which messes things up...

@M.A.R. not lab accurate, more kitchen accurate. Well, specifically for floral preservative

a pH of 3.2 is ideal for water uptake of cut flowers. Citric acid is cheap and effective. So... that's where I'm at.

M.A.R.

@anongoodnurse Do you have solid citric acid or if it's a solution, do you know its concentration?

anongoodnurse

no, crystals, pure (anhydrous?)

so yes, solid.

M.A.R.

OK, working on it

anongoodnurse

Thank you so much! I got 5.5g, but I trust myself with Chemistry like I would trust myself at bullfighting.

Anindya Prithvi

18:23

@M.A.R. Yeah, I see

M.A.R.

@anongoodnurse Sorry, I was distracting myself. So, 5.5 g per what volume of water?

anongoodnurse

@M.A.R. 1000cc

@M.A.R. You scared me! lol!

M.A.R.

Well I find 0.06 g! So let's see

anongoodnurse

I thought you were working on it.

Wow, that's a little bit different!

M.A.R.

I was initially using that master formula, but it had a lot of calculations and I don't have a calculated handy

Safdar

18:30

@M.A.R. Master formula?

anongoodnurse

@Safdar ugh, don't ask.

M.A.R.

So, one key equation is, for weak acids (this is an approximation, the weaker the acid the better): 1/2 pKa - 1/2 log Cm

anongoodnurse

See, I know what 1/2 is, but no idea what Cm is...

M.A.R.

@Safdar Nicolau has a good answer on it if you look around a bit in Acid-Base questions. I assumed two pKa's are important so it's going to be a three-species system but eh forget about it

@anongoodnurse Molar concentration

anongoodnurse

Oh, that makes sense.

M.A.R.

18:32

Another key equation good for approximation is \sqrt([H+]^2 from one species + [H+^2 from another species]) = total [H+]

anongoodnurse

I feel a panic attack coming on... (j/k)

M.A.R.

The second protonation has a smaller pKa but it's significant to around 20 parts in 1000 in calculations

anongoodnurse

@M.A.R. That seems significant then.

M.A.R.

@anongoodnurse Well, the first equation gives the amount of released proton from H4Cit to H3Cit- (One proton gone from citric acid) and the second equation is H3Cit- → H2Cit 2-

anongoodnurse

I wish I had a pH meter... I'd just add citric acid until I had the right pH.

@M.A.R. I do follow, though.

M.A.R.

18:36

So your unknown is Cm, unit mol/L, and you know everything else: [H+] tot will be 10^{-3.2}

anongoodnurse

@M.A.R. Easy for you to say.

You're a chemist, I'm only a physician.

M.A.R.

The values I plugged in are pKa1 = 3.1, pKa2 = 4.7, Molecular mass = 192.124 g/mol

@anongoodnurse HA HA HA funny joke

It's like if a first year med student calls themselves a doctor

anongoodnurse

@M.A.R. yea, I believe that's the correct molecular mass.

Safdar

@M.A.R. chemistry.meta.stackexchange.com/a/4757/95133

anongoodnurse

@M.A.R. My son did that!

Safdar

18:38

Can we just use that and neglect $K_3$

M.A.R.

@anongoodnurse Darn med students :p

anongoodnurse

He would argue medicine with me when he was a year 1!

M.A.R.

We're humbler, we're pharmacy students

You haven't seen me when I'm full of myself though

@anongoodnurse Very med studenty

anongoodnurse

@M.A.R. Oh. Oh... I actually know very little about pharmacy students.

@M.A.R. Are you a male?Gardians of the galaxy?

M.A.R.

We're watchful protectors, silent guardians

@anongoodnurse Yep

Is it showing? :D

anongoodnurse

18:40

No, not at all!

M.A.R.

@anongoodnurse The Dark Knight

anongoodnurse

I was just thinking, you are (no, Guardians of the Galaxy!)

M.A.R.

So, lemme MathJax on the site and show you what I composed in five minutes

anongoodnurse

you are studying to be a pharmacist, not a pharmacologist?

(Pharmacists need to know a lot of basic chemistry, I wager. Doctors only need to have passed the course with a good grade.)

Then promptly leave everything learned behind...

M.A.R.

@anongoodnurse I guess. A study of med and pharmacy students showed that we know a lot of how stuff works, and med students are better at applying it

Wait, whoops, I made a mistake, now I see it.

anongoodnurse

18:44

@M.A.R. hmm...

I don't know why that would be...

Did you know that testosterone (thinking about cocky med students here) makes people cocky?

M.A.R.

I think the study was about pharmacology, specifically

anongoodnurse

Well, confident.

Like that's real news, but it actually is.

M.A.R.

@anongoodnurse If I knew you were male I would've called that a dad joke

anongoodnurse

I'm not a male, I'm an old female! :D

@M.A.R. lol!

It would have been a truly terrible joke.

(wonky keyboard.)

M.A.R.

@anongoodnurse There was the meme that moms come up with dad jokes and it's dads who shamelessly utter them

anongoodnurse

18:47

@M.A.R. hahaha! I believe that!

It does explain a lot about the differences between men and women, though, that extra confidence which is biochemical, not grounded in acquired information...

imho

M.A.R.

Shrug

anongoodnurse

@M.A.R. You've just proven your superiority...

M.A.R.

I'm still like a distracted chicken

So uh, let's pretend those parentheses are the right places

And there's my mistake: I now get log Cm = -0.7

anongoodnurse

@M.A.R. I need to extract citric acid from water?

M.A.R.

Cm = 0.199 mol/L = 38.333 g /L

@anongoodnurse no, dissolve 38.333 grams per liter, which'd be around 4 grams per 100 cc

Math is hating me right now though, so lemme recheck the calculations again

sai-kartik

18:58

@M.A.R. every chemist ever

except the highly skilled ones,ofc

M.A.R.

Rechecked, seems to work out 👀

@sai-kartik what's that

anongoodnurse

@M.A.R. I'm so sorry to have imposed.

I'm desperate, though.

M.A.R.

@anongoodnurse No problem

I wasn't doing anything

sai-kartik

@M.A.R. i meant chemists who are extremely good with their math

anongoodnurse

You're very kind.

M.A.R.

19:00

@sai-kartik I'm joking

sai-kartik

@M.A.R. oops

M.A.R.

@Safdar Oh, just now I noticed this

Safdar

@M.A.R. :|

M.A.R.

@Safdar there there, unsung heroes are among the best heroes.

Except dead heroes.

sai-kartik

@Safdar did you get the haloform question?

M.A.R.

19:04

Even so it seems to expect me to type things.

anongoodnurse

19:15

@M.A.R. - 4 grams per 100 cc? Thank you so much!

M.A.R.

@anongoodnurse The original value I gave you was closer to the correct value, I'm so sorry :( 0.06 g/L, 6 g in 10 mL

According to wikipedia the near saturated solution around room temperature should do it

53 mins ago, by M.A.R.

Well I find 0.06 g! So let's see

19 g / 100 mL would be around pH = 1.8 or 1.9

4 hours later…

Mithoron

23:30

@Safdar You should be more careful with these tag wiki suggested edits. Seems both Tyberius and Matthew are kinda mindlessly accepting them without needed corrections.

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