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### Topic: Proving an acid is dibasic  (Read 96100 times)

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#### merkl

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##### Proving an acid is dibasic
« on: March 21, 2008, 09:39:31 AM »
DELETED:

Answered: and I'd rather not have everyone copying my work.
« Last Edit: May 05, 2008, 05:40:21 PM by Eragon_11 »

#### Borek

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##### Re: Proving an acid is dibasic
« Reply #1 on: March 21, 2008, 10:16:36 AM »
Logical approach is to determine its molar mass and equivalent mass.
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#### merkl

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##### Re: Proving an acid is dibasic
« Reply #2 on: March 21, 2008, 10:55:59 AM »
Molar mass of the acid is 98, and i understand the equivalent mass is half that, but Im lost as to how I go about using that information.

I wonder whether Im supposed to know this method: Ive never been taught it.

#### Arkcon

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##### Re: Proving an acid is dibasic
« Reply #3 on: March 21, 2008, 11:11:28 AM »
Your first post is pretty close, consider, you use the iron reaction to determine how many sulfates the "unknown" molecule has, then you use the titration reaction to find out, "Hmm...molecule can neutralize twice as much NaOH compared to how many sulfates it has" and you're done.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

#### Borek

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##### Re: Proving an acid is dibasic
« Reply #4 on: March 22, 2008, 02:27:41 PM »
All the time your problem is the same - you are trying to do two identical experiments, so they will not give any dirrent information.  Neutralization reaction tells you how many H+ are in sample. H2 tells you how many H+ are in sample. This leads nowhere.

You have to find molar mass of the acid, and mass per one H+ (called equivalent mass). Divide first by the second and you will know number of protons.
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#### merkl

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##### Re: Proving an acid is dibasic
« Reply #5 on: March 22, 2008, 08:13:15 PM »
You raise a good point..my methods in no way prove the acid is dibasic. I missed the point completely.

I understand what you mean by the equivalent mass now, but Im not sure how I could incorporate into a titration/ gas given off experiment as my proof - at the moment it feels like the equivalent mass calculation would be my final proof, but again, I dont know how to come to that conclusion.

I'll continue reading up on it also and try and come up with a method, but any guidance is appreciated.

#### Borek

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##### Re: Proving an acid is dibasic
« Reply #6 on: March 22, 2008, 08:29:23 PM »
Is the limitation (titration/gas collecting) yours, or is it forced upon you? Is it an experiment you are going to make, or the one you have to describe only? And finally - what data do you have as input (ie what do you "know" about sulfuric acid before experiments).
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#### merkl

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##### Re: Proving an acid is dibasic
« Reply #7 on: March 23, 2008, 07:34:35 AM »
It is a set experiment that we have to plan and describe, not actually perform. One method must include titration, the other a gas collection.

We are given the molarity of the acid as being 1.00moldm-3

#### Borek

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##### Re: Proving an acid is dibasic
« Reply #8 on: March 23, 2008, 01:56:31 PM »
We are given the molarity of the acid as being 1.00moldm-3

Well. if you KNOW that solution IS 1 mole per liter, you have to determine number of equivalents in this solution - and this will be answer to your question.
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#### merkl

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##### Re: Proving an acid is dibasic
« Reply #9 on: March 23, 2008, 07:50:36 PM »
And I can do this using both a titration and gas collection? If so, i'll get to thinking about it, and post back when i get somewhere, ( or not, if that so happens to be the case).

EDIT:  would it be possible for you to explain the idea of an equivalent, perhaps in a reaction: i've looked it up on wikipedia, and the article doesnt offer me much that I can understand.

Thanks so far!

#### chrisbb

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##### Re: Proving an acid is dibasic
« Reply #10 on: March 23, 2008, 10:37:05 PM »
This may be a silly question but could you use a potentiometric titration?
just a thought

#### Goud

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##### Re: Proving an acid is dibasic
« Reply #11 on: March 24, 2008, 12:28:57 PM »
Assuming you mean it dissociates into two H+ ions...

-Do a neutralisation titration (using methyl orange or an equivalent as an indicator) of an equal amount (eg: 25ml) of 1M HNO3; 1M HCl and 1M H2SO4 (separately of course), using 1M NaOH.

-Record the volumes of NaOH needed to neutralise each.

-As they are strong acids the monoprotic acids (hydrochloric and nitric) should be within a reasonable margin for error (5%-ish), but roughly the same, showing that they have an equal proportion of H+ ions to be neutralised.

H+ + OH- > H2O

-However the diprotic sulphuric acid (yes I'm English) should react with twice as much NaOH, showing it has twice as many H+ ions.

2H+ + 2OH- > 2H2O
(^needs twice as many OH ions see)

So yeah pretty much what you said, except proving that two monoprotic acids will be the same.

Not sure about the gas, maybe: Metal + Acid > Hydrogen + Salt , but can't think of a great way of doing it off the top of my head. Well, good luck.

#### merkl

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##### Re: Proving an acid is dibasic
« Reply #12 on: March 24, 2008, 01:50:09 PM »
Hey, im English too Didnt know diprotic was actually our way of saying it, but it makes sense.

I like your method though, I understand it fully. I want to see where this equivalent mass idea goes though. It sounds good.

#### saab_101

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##### Re: Proving an acid is dibasic
« Reply #13 on: March 26, 2008, 04:12:43 PM »
hey, im doing the same thing and im not sure either.

but i think for the titration u wld jsut do a regular titration, and then prove it is dibasic by simply working out the stoichiometry os the equation using your titration results.

and for the gas collection, clsdnt u simply react it with, say, iron, and collect the gas using a regular gas collecting method, and then simply work out the moles of hydrogen using the volume of hydrogen given off. but even though im sure im on the right trakck with this one, im not sure how to go about proving it's dibasic from here. wld u work out the number of moles of hydrogen that wld be present for that volume of sulphuric acid if it wasn't dibasic, and then work out the actual number of moles?

#### merkl

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##### Re: Proving an acid is dibasic
« Reply #14 on: March 27, 2008, 07:45:10 AM »
Read my 4th post I think and take a look at my proposed method.

If my idea for both the titration and the gas collection works (and I hope to god it does, because I spent three hours writing it up!) then you also are on the right lines with it.

Granted, it all feels a little bit vague and nothing is quite so conclusive as I'd like - Im still interested in Borek's idea of using equivalent masses, but I', still unsure about how I'd use it.