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Trizocy
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Boiling down Sulpuric Acid
Hey guys! new guy here so hope i can learn from the forum here 
Anyway, i just bought a flask of Drain cleaner which at the back stand 60-100% Sulpuric Acid, and i was wondering if its possible to boil away the
water content inside it?
Goal is not to reach 99% (if its simple, then yes) but to reach a % that i know whats in the bottle
because when im working know, i have no idea if its 60% 80% or 100% inside the bottle....
Thanks!!
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woelen
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What color does it have? It should be colorless, or maybe pale brown. Some very low grade drain cleaner acid is black like soot. I consider that
useless for chemistry experiments.
Normally, drain cleaner is highly concentrated acid, 92% or better, but not more than 98% (higher than 98% H2SO4 is very rare and certainly not
something you will find in a hardware store). Anything at 90% or better can be considered concentrated acid.
Some tests you can do:
- Add a few drops of acid to paper tissue. Does the tissue char and do you get holes in it quickly? If so, then it is well above 90%.
- Add a little acid to table salt. Put a teaspoon full of table salt on a piece of glass and then pour 1 ml of acid on it. Do you see slow bubbling
and a lot of dense white fumes? If so, then the acid is well above 90%.
Concentrating sulphuric acid can be done, but you need heat-resistant lab glassware, a glass-walled thermometer with a range up to 250 C, and a
suitable hot-plate. You also need to do this outside. Concentrating only makes sense if the above two tests fail. Heat the acid in a glass beaker and
put a thermometer in it. Keep on heating until it reaches 200 C or a little bit above that. At that temperature the acid will not simply develop water
vapor, but a more distinct dense white smoke. DO NOT INHALE THIS SMOKE, IT IS EXTREMELY CORROSIVE!
Do this experiment on a breezy day, with wind from behind and assure that if the beaker cracks then no disaster occurs to you or your property (your
heater will be ruined of course). Protect yourself, the very hot concentrated acid is extremely corrosive and it will burn deep holes nearly instantly
in everything! Know what you are doing!
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AJKOER
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I remember an old chemistry text remarking that heated MgSO4 till its red is a substitute for H2SO4 as the anhydrous salt decomposes at 1,124°C. My
take on the thermal decomposition:
MgSO4 ---Heat---) MgO + SO3 (g)
You could investigate the use of other sulfates as well, but be mindful that the SO3 vapor is extremely dangerous as it will react with water vapor
(or the moisture in your lungs) to form some extremely concentrated Sulfuric acid:
SO3 + H2O ---) H2SO4
Best to rethink what you are attempting even via this possibly marginally safer route to pure concentrated Sulfuric acid (I would also recommend you
read some SM's thread of members badly disfigured by acid burns).
[Edited on 16-2-2015 by AJKOER]
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blogfast25
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AJ, behave! There is nothing safe or easy about decomposing MgSO4. And SO3 is notoriously difficult to dissolve in water, which is why they dissolve
it in conc. H2SO4 making oleum and then dilute the oleum.
Concentrating 60 % H2SO4 is not easy though.
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Trizocy
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Hey thanks woelen for fast respond!
Well took a picture of it: http://postimg.org/image/y0nkmq3o9/ (little brown-orange-clear color)
Reaction of tissue : http://postimg.org/image/3qzy5fgnt/
Reaction of salt: http://postimg.org/image/oo6bs56gl/ + lot of fumes
Well got some boro glass, and a mobile hotplate with 1500W, but not a thermometer up to 250 C :/ Will this work out? (also read somewhere that u need
boiling stones?)
How % do you think it is??
AJKQER:
Could you send me one of link of the SM members accidents ?
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AJKOER
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Blogfast, I have since edited my text and while the actual cited reference is valid, I found the comment interesting and remembered it.
Difficult yes, I completely agree (and thank god, I did not want to actually cite more expeditious paths).
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gdflp
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Those all look like good signs, generally sulfuric acid will not react with NaCl unless it is at around 90%+ concentration. In addition, the paper
will only char at a similar concentration. The acid looks remarkably clean by drain cleaner standards, it should work fine for most everything except
very water sensitive reactions where a very high concentration is necessary(e.g. Fischer esterifications) in which case, I would just buy a small
amount of reagent grade sulfuric acid.
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Trizocy
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So we can say its between 90-98% ish?
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gdflp
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Yes. There is some detail here about the second test you did.
[Edited on 2-16-2015 by gdflp]
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woelen
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@Trizocy: Your acid looks very good: both tests show a positve result. It certainly is well above 90% (most likely it is around 95%) and it also looks
clean. No need to concentrate the acid further, tampering with it only degrades its quality. Acid of a concentration above 90% already is
concentrated, you will have a very hard time concentrating it further. Going beyond 96% is impossible without using oleum or SO3.
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Cou
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SO3 is linked to laryngeal cancer in workers.
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Bert
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SO3 is also linked to a rather quicker death from pulmonary edema...
http://www.rtknet.org/node/236
Trizocy:
If you attempt this, please pay CAREFUL attention to Woelen's advice. Do search on this topic here, it has been extensively posted on.
In particular! Please do not place even your borosilicate glass directly on the heating device. USE A SAND BATH. Years ago, I concentrated several
gallons of 30% battery electrolyte using a 4000ml beaker inside a cheap electric deep fryer (purchased for $5.00 at yard sale), first placing an inch
or so of clean dry sand in the fryer, setting the beaker with about 3000ml of electrolyte on the sand, then pouring more sand around the beaker's
walls up nearly to the top of the fryer before beginning to heat the system.
The sand bath heats the beaker of acid evenly, and helps prevent breakage. The fryer is also DESIGNED to operate for long periods at the temperature
levels required, which may destroy some laboratory type hot plates when used with a sand bath.
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Trizocy
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Wowow.. This is great news!
My goal was not to reach 100% or 99% but to know how much sulfuric acid it was in the bottle (%). So i can do some experiment without concern if i put
70% acid to the mixture when its actually 90%
Thanks guys! really helped me out!
Now i know its atleast 90%+ inside it
Quote: Originally posted by woelen  | @Trizocy: Your acid looks very good: both tests show a positve result. It certainly is well above 90% (most likely it is around 95%) and it also looks
clean. No need to concentrate the acid further, tampering with it only degrades its quality. Acid of a concentration above 90% already is
concentrated, you will have a very hard time concentrating it further. Going beyond 96% is impossible without using oleum or SO3.
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Thanks woelen!!, really appreciate it!
95%  , can someone else also confirm this?
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Volanschemia
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| Quote: | | 95% , can someone else also confirm this? |
If you have access to a base like sodium hydroxide and a pH indicator that changes colour at around pH 7, you can perform an acid-base titration to
determine the exact concentration. If you need to know the exact conc, this is a very good way to go.
Do you know how to do a titration?
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and
vapor, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the
Persian king" - Johann Joachim Becher, 1635 to 1682.
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Trizocy
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Hey Austria Scientist!
Well, have ordered a accurate digital PH indicator, so just waiting for it now
Tell me more about : titration?
Thanks
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Volanschemia
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Australian, not Austrian. 
Where'd you get your pH indicator from? That would work very well, better than an indicator as long as it's calibrated correctly.
An acid-base titration is where you can determine the molarity of an acid or base, by neutralizing it with it's opposite (acid if it is a base, base
if it is an acid). It only works if you know the concentration of one of the reactants. So, you want to get the molarity of H2SO4 which is an strong
acid. So you need to neutralize it with a strong base of known concentration. (As a side note, you don't need a strong base but it makes
things a bit simpler). I would suggest Sodium Hydroxide (solid drain cleaner) because it is very easy to get.
So what you need to do is make a solution of Sodium Hydroxide with a known molarity, I would suggest 5M. I'll leave the calculation of how much NaOH
you need up to you. I would suggest making double the volume of H2SO4 you want to titrate. You don't need much, 25mL would be heaps. So make 50mL
of 5M NaOH solution. Now this is very important: Make sure you have exactly 50mL. Using a graduated cylinder with 1mL markings
would work and a burette would be even better. Place the pH meter in the acid and add the NaOH solution until the pH rises to pH 7. Indicating the
acid has been neutralized. You will end up with a solution of Sodium Sulphate according to the reaction below:
H2SO4 + 2NaOH = Na2SO4 + 2H2O
Once you are finished, measure how much NaOH solution you have left and subtract it from your starting amount. This is how much you used.
Now you can calculate the molarity of the H2SO4 via the following equation.
MH2SO4 = VNaOH / VH2SO4 * MNaOH * CH2SO4 / CNaOH
Where C = Coefficient, V = Volume, M = Molarity.
Hope you understood all that!
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and
vapor, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the
Persian king" - Johann Joachim Becher, 1635 to 1682.
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j_sum1
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Titration -- a very basic analytic method. It is as accurate as your ability to measure volume and mass. Acid-base titration is the most basic of
titrations. Basically the idea is that the more concentrated your acid is, the larger the volume of a base solution will be needed to neutralise it.
So, if you prepare some solutions and measure the volume of base needed to neutralise you should be able to calculate the concentration of your acid.
Measure accurately a small amount of your acid. Dilute with water in a flask or beaker. Add some indicator. Phenolphthalein
works well for this. You won't see a colour change. (For accuracy it is better to weigh a larger amount of acid, dilute to a known volume in a
volumetric flask and pipette a small amount of this for your titration.)
Choose a suitable base that will react with your acid. It must be something of high purity that you can measure accurately. Ie, not sodium
hydroxide since that has an unknown amount of absorbed moisture. Anhydrous sodium carbonate would work although it is not ideal since it will release
bubbles. Barium hydroxide would work.
The next step depends a bit on what volumetric measuring equipment you have. A burette is designed for the purpose but you can get an
approximate result with a measuring cylinder or large graduated syringe.
Based on what you estimate your sulfuric acid strength to be, calculate the amount of your base that is needed to react with that amount.
You need to prepare a standard solution of your base to react with the acid you have measured. You need to do some calculations to decide how
concentrated to make this. Ideally, you want the reaction to complete when around half the volume of your burette, measuring cylinder or syringe has
been added to the acid, so work out what that is. For accuracy it is better to weigh out a larger quantity and dilute to a large but known and
accurately measurable amount. Volumetric flasks are designed for this.
Slowly add your base to your acid until you see a colour change (pink in the case of phenolphthalein.) If you swish your beaker you should see
the colour disappear. Then add really slowly until you see the faintest pink colour just stay visible. Record (accurately) the volume of your base
that you used.
Calculations are as follows
Calculate the amount of base used in moles.
Calculate the amount of acid in moles that reacted with that base. This will be proportional to the amount of base in some kind of integer
ratio. You need to have a balanced chemical equation to do this.
Calculate the concentration of the acid you used.
Useful formulas:
converting mass to moles. n= number of moles. m= measured mass. M= molecular mass.
n=m/M
calculating concentration in moles per litre. c=concentration. n=number of moles. v=volume
c=n/v
calculating concentration when diluting. c and v are concentration and volume as before. 1 and 2 are before and after diluting.
c1v1=c2v2
That's it from me. You should be able to find a lot of information on titration with a simple search.
[Ninja'd by Aus Scientist on preview]
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Trizocy
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Hahah sorry about the:" Australian, not Austrian." stuff, i think it was the sandman, sparking some dust on my eyes
The PH indicator is bought from alibaba.
Okay, this was interesting, just wanna say that my science skills is not the best, so hope anyone help me out.
Everytime i read it, i understand it more and more 
Anyway, (newbie question) about molarity, is that the concentration of the sulf acid in the bottle?
And what is Coeffecient?
You said: "I would suggest 5M of Sodium Hydroxide solution" does this works then:?
100% NaOH powder
25ml total, 23,75ml water and 1.25ml NaOH powder = 5M or 5%, am i on right track ?
Have 10ml ,5ml and even 1ml pippets if that would work
Could you maybe give a calculation example?
Thanks, really appreciate, "Australian"Scientist
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aga
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Right now i have 500ml of H2SO4, and Clear (not brown) from a bottle of Brown Drain Cleaner.
Add 3% OTC H2O2 and stir while heating (it spits a lot) and all the brown goes away.
The Brown is not a problem at all, but it just does not look as good.
Heat some more until the acid starts fuming ; you will definitely know when it is not water leaving the pot anymore, and you have Clear, 98% H2SO4.
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aga
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This belongs in the Beginnings topic.
'Molarity' refers to the number of Molecules of whatever in a litre.
Google and Wiki : http://en.wikipedia.org/wiki/Molar_concentration
Understanding Molecular Weights and Molar Concentration is a very good thing to do.
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Volanschemia
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| Quote: Originally posted by Trizocy | Hahah sorry about the:" Australian, not Austrian." stuff, i think it was the sandman, sparking some dust on my eyes
The PH indicator is bought from alibaba.
Okay, this was interesting, just wanna say that my science skills is not the best, so hope anyone help me out.
Everytime i read it, i understand it more and more
Anyway, (newbie question) about molarity, is that the concentration of the sulf acid in the bottle?
And what is Coeffecient?
You said: "I would suggest 5M of Sodium Hydroxide solution" does this works then:?
100% NaOH powder
25ml total, 23,75ml water and 1.25ml NaOH powder = 5M or 5%, am i on right track ?
Have 10ml ,5ml and even 1ml pippets if that would work
Could you maybe give a calculation example?
Thanks, really appreciate, "Australian"Scientist
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Chemistry is a great hobby to get into, you pretty much never stop learning!
Like Aga said, molarity is the number of Moles of a molecule per Litre of solvent.
1 Mole is Avogadro's number: 6.022*10 to the 23rd power.
So 5M NaOH solution would be a solution that contains 5 * Avogadro's number NaOH molecules per L of solvent (in this case, water).
Molarity is not percentage, which gets a lot of people confused.
To figure out Molarity, you first need to molecular weight of the compound in question. NaOH's molecular weight is 39.9971g/mol. Meaning 1 Mole of
NaOH molecules would weigh 39.9971g. So if you were to dissolve 39.9971g of NaOH in 1L of water, you would end up with a 1M solution!
So for 5M we just multiply NaOH's molecular weight by 5, giving us 199.9855g. Let's just say we need 200g. Since we don't need a full Litre, we
divide. We're after 50mL. 1000/2 = 500 / 10 = 50. 200/2 = 100 / 10 = 10g of NaOH in 50mL of water to make a 5M solution. Make sure you have an
accurate set of scales for weighing the NaOH.
Coefficient is the number beside a reactant or product in a reaction equation. For example in the following equation:
2H2 + O2 = 2H2O
The "2" before the Hydrogen and the Water are the coefficient. So the equation is saying 2 Hydrogens react with one Oxygen to give 2 Waters.
What are the measurement increments on your pipettes? They may work, but I'm not sure about the accuracy of pipettes. A syringe might be better and
a grad cylinder would be perfect if you have one.
OK, a calculation example.
I have an some OTC HCl and I don't know the concentration. I have some NaOH solution that I know is 5M.
I measure out 25mL of the HCl in a beaker and add an indicator that will change colour at pH 7 (or in your case, a pH meter). I then add the NaOH in
small amounts until the indicator changes colour (or the pH meter hits 7). I then measure how much NaOH solution I used. Let's just say I used 30mL.
The reaction equation for HCl/NaOH neutralization is:
HCl + NaOH = NaCl + H2O
(If there is no coefficient number, the coefficient is one)
Equation:
MHCl = VNaOH / VHCl * MNaOH * CHCl / CNaOH
MHCl = 30 / 25 * 5 * 1 / 1
MHCl = 6
[Edited on 17-2-2015 by TheAustralianScientist]
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and
vapor, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the
Persian king" - Johann Joachim Becher, 1635 to 1682.
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Trizocy
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| Quote: Originally posted by TheAustralianScientist |
Chemistry is a great hobby to get into, you pretty much never stop learning!
Like Aga said, molarity is the number of Moles of a molecule per Litre of solvent.
1 Mole is Avogadro's number: 6.022*10 to the 23rd power.
So 5M NaOH solution would be a solution that contains 5 * Avogadro's number NaOH molecules per L of solvent (in this case, water).
Molarity is not percentage, which gets a lot of people confused.
To figure out Molarity, you first need to molecular weight of the compound in question. NaOH's molecular weight is 39.9971g/mol. Meaning 1 Mole of
NaOH molecules would weigh 39.9971g. So if you were to dissolve 39.9971g of NaOH in 1L of water, you would end up with a 1M solution!
So for 5M we just multiply NaOH's molecular weight by 5, giving us 199.9855g. Let's just say we need 200g. Since we don't need a full Litre, we
divide. We're after 50mL. 1000/2 = 500 / 10 = 50. 200/2 = 100 / 10 = 10g of NaOH in 50mL of water to make a 5M solution. Make sure you have an
accurate set of scales for weighing the NaOH.
Coefficient is the number beside a reactant or product in a reaction equation. For example in the following equation:
2H2 + O2 = 2H2O
The "2" before the Hydrogen and the Water are the coefficient. So the equation is saying 2 Hydrogens react with one Oxygen to give 2 Waters.
What are the measurement increments on your pipettes? They may work, but I'm not sure about the accuracy of pipettes. A syringe might be better and
a grad cylinder would be perfect if you have one.
OK, a calculation example.
I have an some OTC HCl and I don't know the concentration. I have some NaOH solution that I know is 5M.
I measure out 25mL of the HCl in a beaker and add an indicator that will change colour at pH 7 (or in your case, a pH meter). I then add the NaOH in
small amounts until the indicator changes colour (or the pH meter hits 7). I then measure how much NaOH solution I used. Let's just say I used 30mL.
The reaction equation for HCl/NaOH neutralization is:
HCl + NaOH = NaCl + H2O
(If there is no coefficient number, the coefficient is one)
Equation:
MHCl = VNaOH / VHCl * MNaOH * CHCl / CNaOH
MHCl = 30 / 25 * 5 * 1 / 1
MHCl = 6
[Edited on 17-2-2015 by TheAustralianScientist] |
Hey
Thanks for the example, really learnt much here but got some questions:
- Will a 0,00g scales works? or do i need a 0,0000g?
- Well the pipettes looks like this, but i will try to find and buy a burette, also heard that pycnometer is good to measure also, what do u think?
- I see you used HCI as a example this time, does NaOH work on every acid?
I think im still one of them, . how much concentration is it in 6M HCI? Because u
said :"acid-base titration to determine the exact concentration."
But i only know how much Moles in it now.
Just want to say thanks for your effort, really appreciate it
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Volanschemia
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You're welcome. I'm glad I can teach you.
0.00g scales will work fine.
Those pipettes actually look very accurate. The 10mL one would be best I think. You won't need to use it to measure out the 50mL of solution to
begin with, a rough amount is fine. But for the titration I think it would work well. Just add the solution in 10mL increments until the pH gets to
about 5 and then go slower and slower until you hit 7 exactly. Make sure you record the exact amount of NaOH solution used.
As a side note, make sure your pH meter is calibrated before you measure or it could be very off. Is it just a portable meter or a computerized one?
A think a pycnometer measures relative density, not volume.
NaOH is a strong base which means it is great for titrating against any strong acid (eg. H2SO4, HCl, HNO3, HF) but not perfect for weak acids (eg.
Acetic Acid, Citric Acid). For those you want a weak base like ammonia. You can titrate with a strong/weak combination but it requires a different
pH indicator.
Molarity is usually more important to a chemist than percentage, but it is easy to convert. First you need the molar mass of the substance. So HCl =
36.46g/mol. We have 6M solution of HCl so 6 * 36.46 = 218.76g of HCl in 1L of solvent. From there it is easy to get percentage. 218.76 / 100 =
0.21876 or 21.876% w/v.
"The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and
vapor, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the
Persian king" - Johann Joachim Becher, 1635 to 1682.
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Chemosynthesis
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| Quote: Originally posted by Trizocy |
Hey
Thanks for the example, really learnt much here but got some questions:
- Will a 0,00g scales works? or do i need a 0,0000g? |
My opinion is that 0.00g scales are fine, and 0.000g scales are great. Anything more accurate than that gets into analytical equipment, and while
nice, is probably excessive and expensive.
| Quote: | | - I see you used HCI as a example this time, does NaOH work on every acid? |
Yes. Arguably any strong base could work on any strength acid. The reason you want to use NaOH is that it essentially completely dissociates. This
makes it easy to correlate neutralization of acid with quantity of base for comparisons.
| Quote: | I think im still one of them, . how much concentration is it in 6M HCI? Because u
said :"acid-base titration to determine the exact concentration."
But i only know how much Moles in it now.
|
There is more than one type of concentration. Which one you want to use can vary.
If you want a mass concentration, you need to take moles of your solute and convert to mass of solute. Now divide this by the volume of solvent to
find out what mass of substance is in what volume of solvent.
Volume concentrations get a little more complicated because, surprisingly, adding two liquids together, or a liquid and a solid, is often slightly
different from the sum of the separate components. For this reason, it's often used to approximate mass concentration due to convenience of pouring
rather than taring and weighing.
Once you have those down, you might look into molality... which is different from molarity. But not until you're comfortable.
Edit- oops, Australian Scientist posted an excellent post while I was typing, making this pretty irrelevant. Just listen to him.
[Edited on 17-2-2015 by Chemosynthesis]
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Trizocy
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Hmm, interesting.
"Is it just a portable meter or a computerized one?"
- Its a portable, with temp and ph meter
"Molarity is usually more important to a chemist than percentage"
- May i ask why? would it not be better to say: yup this bottle is 100% acid ? than 281/mols in it ?
Thanks, waiting for the ph meter to arrive, so gonna do a try, will keep you updated
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