Chemistry Problem

[joml88]

This problem seems really easy (and probably is) but I am troubled by it for some reason. I can't remember it exactly because it was on a test in my high school chem. class today.

What is the pH of a solution that has 12.00 g Na(OH)2 and 250.0 mL H2O?

[joml88]

Hmm, no one wanted to help. O well I got my test back and I got it right. I asked this question because the pH was about 14.07. While I was taking the test I thought that it was ok to have a pH above 14 but wasn't sure.

[admiral_ju00]

Hmm, no one wanted to help. O well I got my test back and I got it right. I asked this question because the pH was about 14.07. While I was taking the test I thought that it was ok to have a pH above 14 but wasn't sure.

 

or maybe you didn't leave enough time for someone to find this question and answer?

[joml88]

Yeah, but this forum is called the homework help forum. Unless it's a project you usually don't have much time for the problems(one day most of the time). I was expecting a reply before I got the test back but since I got the test back first I just told everyone that help wasn't needed anymore.

[wolfson]

This problem seems really easy (and probably is) but I am troubled by it for some reason. I can't remember it exactly because it was on a test in my high school chem. class today.

What is the pH of a solution that has 12.00 g Na(OH)2 and 250.0 mL H2O?

 

Firstly find out the molarity:

 

Molarity = Number of moles (n) x Volume (dm^3 or L)

 

So:

 

Number of moles = Atomic mass of compound / mass you have

 

therefore

 

n = (22.99 (Na) + 15.99 (O) + 1 (H)) = 39.98g

 

Therefore:

 

n = 12.00 / 39.98 = 0.300 Moles

 

Then molarity

 

Molarity = Number of moles (n) x Volume (dm^3 or L)

 

therefore:

 

M = 0.300 x 0.250 = 0.075 M.

 

Then calculate pH for a base and REMEMBER there are two molecules of OH so:

 

pH(Lx_n) = 0.075 x 2 = 0.15 M (new pH calculative molarity)

 

Thus:

 

pH(base) = Molarity / Water constant (1.0e14)

 

pH(base) = 0.15 / 1.0e14) = 0.0000000000000015

 

then pH = -Log(final M)

 

pH = -Log(0.0000000000000015 (15e-15) = 14.82

 

And the pH of an acid or base has an Infinite level.

[aommaster]

So, an acid can go below 0?

[wolfson]

Yes -2 or even lower they do not have a limit.

[aommaster]

oh wow, imagine an acid with -100 as a pH!!!

[wolfson]

Dangerous id say, id keep away lol.

[aommaster]

Do you really think there is such a thing? It is possible, of course, but what acid has the lowest pH?

[J'Dona]

Ouch... a solution with a pH of -100 would be an H⁺ concentration of 10¹⁰⁰ mol dm^-3. At that concentration I think the protons would repel each other so much and with so much energy that the solution would explode and probably destroy the Earth with it.

[aommaster]

probably destroy the Earth with it

 

I hope that was an exaggeration!

[J'Dona]

Not really... I heard somewhere that there's about 10⁸⁰ fundamental articles in the universe (a googol). Even a cubic micrometer of this solution contains more protons than that, so if you had any significant amount of this solution it ould be quite nasty. Actually, this thing would contain something ridiculously stupid like 10⁵⁸ protons in one cubic femtometer (about the same distance as between protons in a nucleus), and at that point even the strong nuclear force would be repelling them as well as the electromagnetic. The result would be a very nasty explosion, I do believe, bearing in mind that this amount of protons has about the same mass as the Earth or thereabouts...

[Crash]

They can go that low, thoeritically but realistically i dont think they go past -1 (HF)

Does anyone know of pH's below this? of an actual acid not just different concentrations of Hydronium

[aommaster]

What about alkalis? What is the highest they go up to? I think it is of pH 14 or soemthing, by sodium, lithium and potassium hydroxide or something

[J'Dona]

Well... an alkali equivalent to the hyperacid mentioned earlier would hav a pH of about 114, which means that for just about any volume you want to choose (anything that fits into the universe anyway) you get approximately zero H⁺ ions. Since it only has a pH like that when it contains some water, you'd have to find some way to stop the reversible reaction where H₂0 becomes H⁺ and OH^- and vice versa, then completely remove all the H² ions from it. I suppose that water at absolute zero would be like that, as the alkali of water decreases as temperature decreases, but I thought it was theoretically impossible to get something to absolute zero, and you wouldn't be able to do anything with it even if you could. :/

[aommaster]

No, not a hyperacid that would destroy the world Just the strongest alkali that was made?

[J'Dona]

I don't know how strong the strongest alkali they've eever made is. An alkali is really just a solution with a very low H⁺ concentration instead of a very high one, so the principle would be the same except that the species in the solution were accepting protons instead of donating them. So if the solution were the same in principle, the OH^- ions would repel and still destroy the Earth. :S

 

I've just tried looking of Google for the strongest alkali, but I can't find anything. :/ There's something about CsOH being the strongest, though I can't confirm that, and I don't know the pH of it anyway...

[aommaster]

I tihkn most alkali metals, when reacted with water, form a strong alkali soultion of pH 14 or something. I don't know whether that was a rule or not however

[wolfson]

Remember that a pH of any strong acid can go low, HF is a weak acid, HCL with a high molarity can go -2. But the strongest acid on Planet Earth is H(CB11H6Cl6), but HClO4, HCl, H2SO4, and HNO3 are also very strong.

[YT2095]

But the strongest acid on Planet Earth is H(CB11H6Cl6)

just out of curiosity, what is it called?

[aommaster]

Probably hydro carbo something chloric acid!!!!

[YT2095]

don`t forget the Boron

 

edit: maybe Carborocloric acid? LOL )

[aommaster]

I was wondering what The B was. I forgot it!

[YT2095]

well it may even have a "Hydro" prefix, making it Hydrocarborochloric acid? heheheheheh, and before anyone takes this seriously, we are ONLY GUESSING at names until Wolfson comes back with the answer.

 

 

there`s no real need for anymore input here unless you KNOW the real answer, otherwise the thread goes down the "Off Topic" pan