Little_Ghost_again
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When is a solution considered concentrated
Hi
Ok real noob question, I understand now how to work out how many mols in a solution etc. But what I dont understand is what constitutes a concentrated
solution.
For example Sodium Hydroxide...... 100ml of 1M solution. Is this considered concentrated or dilute?
At what point does a solution change from being classed as dilute to concentrated?
I might not be explaining this well so sorry for that, one final example
Say I wanted a dilute solution of sodium hydroxide and a concentrated one, how many Mols would be in each 
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plante1999
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Concentrated solution is quite arbitrary, in general, everything over 50% conc. is considered concentrated, but it varies following the compound.
Conc. sulphuric acid is generally over 90%
Conc. nitric acid is generally over 60%
Conc. Hydrochloric acid is generally over 30%
etc...
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Tdep
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Ah, it's all relative. When is something big? Everything is huge compared to quarks 
If a solution is close to being saturated, it's pretty concentrated.
But if you're used to working with 0.001mol/L solutions, 0.1mol/L solutions seem pretty concentrated. It only works in context really.
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Little_Ghost_again
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Hmmm that can be a bit of a problem then. For example often I see things like add concentrated sulfuric acid or whatever.
To be fair you even see old reagent bottles with frosted glass labels saying Conc Sulfuric Acid or Dilute Sulfuric Acid (I have some of these old
bottles). Strange that in an area of Science like chemistry a common term is so arbitrary. I was sure some one was going to say x% and over is Con.
Oh well new rule of thumb over 50% conc unless its a chemical in which case just pick a figure lol.
I guess if I look at the solubility figures for a chemical then work out the Mols of the solution in grams that should give me a rough guide.
Curiosity question, why 30% for hydrochloric acid? what starts to happen to it to make the figure so low? What I am getting at is 30% is a pretty low
figure, so there must be a reason why hydrochloric acid dosnt come at say 99%.
Another thought occurred to me.....why use concentration instead of saturation? saturation would make more sense wouldn't it? This solution is @ 85%
saturation @x temp.
Ok looks like pain killers making me talk bollocks! I will just say thanks and remain confused
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Mailinmypocket
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HCl at 100% is a gas, it can only dissolve in water up to a certain extent, con. HCl is usually closer to 37-38% though. Similar to ammonia solutions,
they start to max out at around 28-30% as ammonia is also a gas with solubility limits in water...
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plante1999
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Conc. Ammonia is over 20% generally, like Mail said, it is due to the fact some compounds are gas and have a maximum solubility limit.
Same for most solid and azeotrope.
[Edited on 24-9-2014 by plante1999]
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Little_Ghost_again
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Thanks that clears a few things up
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Nicodem
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A solution is concentrated after it has been concentrated.
A solution is diluted after it has been diluted.
Do we really have to have threads like this, discussing the semantics that can be checked in any dictionary?
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Little_Ghost_again
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Look this isnt semantics! I am not a stupid kid. I am learning about molar solutions etc. That I understand, I understand the term concentrated. I
also have reagent bottles with concentrated printed on them. What I was asking is if there was a way to quantify concentration i.e over 50%.
So where in the dictionary you linked too does it explain that concentrated Hydrochloric Acid is 30% and concentrated Sulfuric is 90%?
No idea what your problem is but I think I asked an intelligent question in the beginners section, a place I would consider it was ok to ask basic
questions.
You took the time to post a link that tells me nothing about what I asked.
I apologize if you misunderstood my post, if you didnt then your reply was pointless
EDIT
Its ok I just read a random selection of your posts.. I thought you were picking on me, I didnt know you were just one those kind of people.
Well lets face it everyone has one so I guess there is bound to be a few spares in the world 
[Edited on 24-9-2014 by Little_Ghost_again]
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Nicodem
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There is no such way. The terms concentrated/diluted only refer to the action taken. The meaning is subjective. For example, you can dilute at
infinitum. Or you can concentrate to the pure material. In no case can you quantify the the meaning of the act without defining it on the spot.
In certain cases, concentration with a specific method under certain conditions has its limitations and thus the limiting concentration got its
trivial meaning. For example, you can concentrate aqueous nitric acid to its azeotrope composition of about 65% using atmospheric distillation. Or
sulfuric acid to 98%, and so on. However, these values are not quantification of the term concentrated, they are just a trivialization.
| Quote: | | So where in the dictionary you linked too does it explain that concentrated Hydrochloric Acid is 30% and concentrated Sulfuric is 90%?
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Concentrated hydrochloric acid is not 30% and concentrated sulfuric acid is not 90%, unless there is a historical record of the batch being made by
concentrating them from a lower initial concentration. So, if you concentrate your 35% acid to 90%, then your sulfuric acid is concentrated.
Analogously, if you dilute your 98% acid to 90%, then your sulfuric acid is diluted. Just like the dictionary says.
| Quote: | | You took the time to post a link that tells me nothing about what I asked. |
On the contrary, the dictionary definitions No. 3 are straight to the point and describe everything in a single line of text. Why would I waste as
much time as I did for this post, when you can just read those two definitions and understand the same concept, assuming the minimum of intelligence
required on the receiver’s end (my assumptions are often wrong, but I keep on trying and sometimes I'm proven right).
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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plante1999
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Nicodem, I know you like to be precise in the way you explain things, but let's face it, this trivia is an important part of modern chemistry, even if
98% sulphuric acid is concentrated sulphuric, nowadays, it is mostly made with oleum, which mean we could call it diluted, however, in practice we
call it concentrated.
Youngs won't catch up by being so nitpicking about terms that have been used in chemistry for a long time, even if they are trivia and not based on
the definition of the dictionary.
Concentration was and is still arbitrary given for each compound by chemists based on saturation/azeotrope generally.
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Little_Ghost_again
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Quote: Originally posted by Nicodem  |
There is no such way. The terms concentrated/diluted only refer to the action taken. The meaning is subjective. For example, you can dilute at
infinitum. Or you can concentrate to the pure material. In no case can you quantify the the meaning of the act without defining it on the spot.
In certain cases, concentration with a specific method under certain conditions has its limitations and thus the limiting concentration got its
trivial meaning. For example, you can concentrate aqueous nitric acid to its azeotrope composition of about 65% using atmospheric distillation. Or
sulfuric acid to 98%, and so on. However, these values are not quantification of the term concentrated, they are just a trivialization.
| Quote: | | So where in the dictionary you linked too does it explain that concentrated Hydrochloric Acid is 30% and concentrated Sulfuric is 90%?
|
Concentrated hydrochloric acid is not 30% and concentrated sulfuric acid is not 90%, unless there is a historical record of the batch being made by
concentrating them from a lower initial concentration. So, if you concentrate your 35% acid to 90%, then your sulfuric acid is concentrated.
Analogously, if you dilute your 98% acid to 90%, then your sulfuric acid is diluted. Just like the dictionary says.
| Quote: | | You took the time to post a link that tells me nothing about what I asked. |
On the contrary, the dictionary definitions No. 3 are straight to the point and describe everything in a single line of text. Why would I waste as
much time as I did for this post, when you can just read those two definitions and understand the same concept, assuming the minimum of intelligence
required on the receiver’s end (my assumptions are often wrong, but I keep on trying and sometimes I'm proven right). |
By the time you had posted I already understood, the point (if there was any) was that having reagent bottles (these are really old) with conc Acid
frosted on them are kind of pointless, with Aga's help I got my head around Mols.
But even in some of your posts you use the term Concentrated, but as you point out that is kind of like saying Big. Use a big amount of solid, this
bottle contains a big amount of powder.
Actually none of this is your fault,you will not see or understand why this mattered to me. There may well be people who read this and have kids or
contact with kids with aspergers, they are likely to get what I mean.
So a little return knowledge as a thank you for taking the time to repost.
Tell someone with aspergers that science deals with facts and figures, tell them that measurements matter and so does accuracy. They will except this
as law, tell them what a mol is,this will and does make sense to them.
Tell them its concentrated.............. each and everyone will ask how many mols are in a concentrated solution.
So to the point
Am I stupid?
Well on the one hand I am top in most subjects at School, despite large amounts of time off, but again that could be subjective as it relies on how
smart the others are.
I get very high scores in certain IQ test's (most aspergers do).
Idiot savants/Savantes (female) are all aspergers syndrome. So on the one hand yes I might be an idiot compared to you or others, but then again I
might be better than you r anyone else at something different.
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vmelkon
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In reality, you can't dilute to infinitum since materials are quantized. The lowest concentration would be 1 molecule per whatever the size of your
liquid/gas/solid is.
Signature ==== Is this my youtube page? https://www.youtube.com/watch?v=tA5PYtul5aU
We must attach the electrodes of knowledge to the nipples of ignorance and give a few good jolts.
Yes my evolutionary friends. We are all homos here. |
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