Chemical Forums
Specialty Chemistry Forums => Citizen Chemist => Topic started by: Trizocy on February 09, 2015, 05:21:36 AM
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Hey
Looking for some help, are new to chemi so need help to find concentration.
I want to know how it works, so i got 1L bottle of Ammonia, on the description it stand 25%
How do you calculate it to 25%?
Tryed the destiny method but did not work.
Had a beaker with 50ml weight 44,65g.
Anyone can help me out :)?
Thanks
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How do you calculate it to 25%?
You don't, it is given. Someone else checked what the concentration is.
Tryed the destiny method but did not work.
Please elaborate, no idea what you mean.
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Okay, forget about the density method :P
Anyway, if i got 1L of ammonia and dont know what % of ammonia is in it, how do i calculate how much % is it?
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You don't calculate the concentration - you determine it experimentally.
Calculation is part of the procedure but without some kind of measurement you can't do anything.
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What kind of measurement do you mean then?
All i want to know is how much ammonia (NH3) there is in the 1L bottle.
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Anyway, if i got 1L of ammonia and dont know what % of ammonia is in it, how do i calculate how much % is it?
All i want to know is how much ammonia (NH3) there is in the 1L bottle.
Previously you have stated you don't know the concentration. If you don't know the concentration you can't pull it out of a thin air by some magical "calculations".
Chances are your question is "how much ammonia is in 1 L bottle of 25% solution", but so far you have failed to ask it. Instead you have mentioned
the destiny method
perhaps meaning "I know the density, which is necessary to calculate mass of the solution", but I can only guess.
Sorry, you have to be precise about what you know and what you are looking for. I don't see this thread arriving at any destiny with that density of mistakes.
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Hey Borek,
Sorry, my English is not the best, and are relative new in the chemical stuff. I will try to be more precise this time :)
Okay, i saw a youtube video where some guy was concentrating Nitric acid, and when he was done concentrating, he put 0,6ml of the Nitric acid into a glass cylinder which gave 0,902 g. And the density of 100% Nitric acid is 1,51grams per ml, so here is the density method i call:
0,902g * 0,6ml = 1,503
1.503 / 1.51 * 100 = 99.54%
So yeah, the Nitric acid was 99%, okay then i wanted to try this method on my 1L ammonia bottle
100% Ammonia = 0.86 density (according to wiki)
So i put 50ml into a breaker, which gave 44,65g
Calculation:
0,4465g * 0,5ml = 0,22325g
0.22325 / 0.86 * 100 = 25.96% Ammonia
PS: hmm while i wrote this reply, it seems like the calculation was right this time, because the description on the bottle says 25% and my result is 25,96%
Anyway, is this a correct and good way to find the %?
If this is wrong again, please help me out :-\ (Hope you get my point this time Borek ;) )
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Okay, since the ammonia calculation did right, then i wanted to try a 1L bottle of Isopropyl alcohol (on the description it stand 99% 2-propanol)
100% density of Isopropyl alcohol is 0.786 g per ml.
So i put 5ml in a beaker and weight it, and gave me 38,45g
0,3845g * 0,5ml = 0,19225
0.19225 / 0.786 * 100 = 24.46% of 2-propanol in the 1L bottle ???
Wrong? ,then i tryed to divide instead of multiply:
0,3845g / 0,5ml = 0,769
0.769 / 0.786 * 100 = 97.84% This time, it seems was much better, but why divide on this and not multiply? and is this right calculation?
Gonna try this calculation on a plumber-cleaning bottle (contain 60-90% sulfuric acid)
I am happy to know if anyone can confirm this method :)
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I am not going to comment on "what some guy on youtube did" not seeing the video, but what you listed doesn't make much sense.
100% Ammonia = 0.86 density (according to wiki)
What units? It is the density of a liquid ammonia, or of a gaseous ammonia? If of a liquid ammonia - is it the same as ammonia solution, or is it something completely different?
So i put 50ml into a breaker, which gave 44,65g
OK, so you did an experimental measurement, that's good.
Calculation:
0,4465g * 0,5ml = 0,22325g
You can't multiply grams per mL and get grams.
0.22325 / 0.86 * 100 = 25.96% Ammonia
Sorry, but this is a random number, not even closely related to what you are trying to find.
The only way to check the solution concentration from your measurement is to calculate the density (you have both mass and volume), and find the related concentration in the density tables.
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I am happy to know if anyone can confirm this method :)
No, its is wrong.
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Hey Borek ;D
Quote from: Trizocy on Today at 09:15:34 AM
100% Ammonia = 0.86 density (according to wiki)
What units? It is the density of a liquid ammonia, or of a gaseous ammonia? If of a liquid ammonia - is it the same as ammonia solution, or is it something completely different?
Well, i look up at wikipedia and there is stand: Density 1.84 g/cm3, liquid form. yeah and its the same as ammonia solution
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Calculation:
0,4465g * 0,5ml = 0,22325g
You can't multiply grams per mL and get grams.
Haha, did not mean gram, but density ;) thanks for correcting me
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0.22325 / 0.86 * 100 = 25.96% Ammonia
Sorry, but this is a random number, not even closely related to what you are trying to find.
The only way to check the solution concentration from your measurement is to calculate the density (you have both mass and volume), and find the related concentration in the density tables.
Okay can you try to help me to find the solution concentration? have aldready write the mass and volume, do you need to know anything more?
Thanks ;)
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Hehe tryed the sulfuric acid also, but the number was 105% (60%-100%) so think my calculation is completely wrong ;D ;D
Can someone help me out
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Well, i look up at wikipedia and there is stand: Density 1.84 g/cm3, liquid form.
No, it doesn't say that. 1.84 g/mL looks more like the density of the pure sulfuric acid. But these densities are of no use here. Mostly because
and its the same as ammonia solution
ammonia solution and liquid ammonia are two different things.
The only way to check the solution concentration from your measurement is to calculate the density (you have both mass and volume), and find the related concentration in the density tables.
Okay can you try to help me to find the solution concentration? have aldready write the mass and volume, do you need to know anything more?
Which part of what I told you to do is unclear?
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Hey Borek
Well, i look up at wikipedia and there is stand: Density 1.84 g/cm3, liquid form.
No, it doesn't say that. 1.84 g/mL looks more like the density of the pure sulfuric acid. But these densities are of no use here. Mostly because
Yeah you had right sorry, had 3 wiki pages up, two of them was ammonia and sulfuric acid, so must have exchanged them ;)
and its the same as ammonia solution
ammonia solution and liquid ammonia are two different things.
Did some lookup on the product, and on a pdf file does it stand it contains 25% ammonia solution
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Quote
The only way to check the solution concentration from your measurement is to calculate the density (you have both mass and volume), and find the related concentration in the density tables.
Okay can you try to help me to find the solution concentration? have aldready write the mass and volume, do you need to know anything more?
Which part of what I told you to do is unclear?
I think the whole part was unclear, could you give me an example?
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ammonia solution and liquid ammonia are two different things.
Did some lookup on the product, and on a pdf file does it stand it contains 25% ammonia solution
It still doesn't mean liquid ammonia and ammonia solution are the same thing. Liquid ammonia is a liquefied gas, ammonia solution is the ammonia dissolved in water. Completely unrelated concepts.
I think the whole part was unclear, could you give me an example?
Imagine you have weighed 100 mL of the ammonia solution, and it turned out its weight is 95.91 g. That means the density is 95.91 g/ 100 mL = 0.9591 g/mL
Google for an ammonia solution density table:
http://www.scribd.com/doc/30212886/Aqua-Ammonia-Specific-Gravity-Chart#scribd
There is no 0.9591 g/mL on the list, but it is apparently between 0.9605 g/mL (9.83%) and 0.9589 g/mL (10.28%). Your solution is more or less 10%.
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Quote from: Trizocy on Today at 12:49:32 PM
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ammonia solution and liquid ammonia are two different things.
Did some lookup on the product, and on a pdf file does it stand it contains 25% ammonia solution
It still doesn't mean liquid ammonia and ammonia solution are the same thing. Liquid ammonia is a liquefied gas, ammonia solution is the ammonia dissolved in water. Completely unrelated concepts.
Yeah sorry, got the concept now, its no liquid ammonia, only ammonia solution :)
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I think the whole part was unclear, could you give me an example?
Imagine you have weighed 100 mL of the ammonia solution, and it turned out its weight is 95.91 g. That means the density is 95.91 g/ 100 mL = 0.9591 g/mL
Google for an ammonia solution density table:
http://www.scribd.com/doc/30212886/Aqua-Ammonia-Specific-Gravity-Chart#scribd
There is no 0.9591 g/mL on the list, but it is apparently between 0.9605 g/mL (9.83%) and 0.9589 g/mL (10.28%). Your solution is more or less 10%.
Thanks!!, something that really helps!
Okay, since i weight 44,65g from 50ml then i do calculation like this?
44,65g*2 = 89,3g
then we got 89,3g weight on 100 ml
89,3g /100ml = 0,893 g/ml
0,893 g/ml is between 0.8931 (30,87%) and 0.8946 (30,38%)
but since 0,893 g/ml and 0.8931 (30,87%) is so really close then we can call it 30ish%
But this is 5%(bottle says 25%) more than the description on my ammonia bottle?
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Tryed also with the Isopropyl alcohol
38,45g * 2 = 76,9g
76,9g / 100ml = 0,769 g/ml
And on the density table http://www.pharmcoaaper.com/pages/TechLibrary/tech_docs_high_purity_solvents_reagent_chem/specific_gravity_isopropyl_alcohol_water_mix.pdf
there is no 0,769 only 0,7861 which is 100% ;/
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Good. You have a proper density table, and you've got some definitely anomalous results. I was actually waiting for this to happen to you, so we can talk more about your technique.
Density is mass divided by volume. You know this. But how do you get mass? And how are you determining volume? Above you said you worked with 50 ml, but measured how? Did you use a beaker to the 50 ml line? Or a graduated cylinder to its 50 mL line? Or did you use a pycnometer, which is the only way to be truly accurate?
Here's an experiment for you. Determine the density of distilled water. Do it 10 times, (or 20, or 50 or 100, if you're dedicated enough.) You can determine your accuracy -- the density of water, at 25 °C (you have been controlling the temperature all along, correct? Density varies with temperature,) is defined as 0.997. How close to this number is your average of ten trials? What is your precision? That can be defined as the standard deviation (most calculators and Excel will compute that for you,) in simple terms. How good are you at getting close to the same number over multiple trials. That will tell how good any one trial of your is.
This is what science is, and I'm saddened that no one seems to know this. Lately, particularly on this board, the definition of "fun" science is "Look at me, I can make drugs, but I'd never take them, but Whee, I'm awesome" or "Look at me, I can make the ingredients for bombs, but I'm totally not a terrrrist, but lookithow awesome I am." If you want to try to understand the anomalous results, checking your abilities is a good place to start.
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Greetings Arkcon and welcome to the conversation, you actually gave me a smile on the face at your last reply
But how do you get mass? And how are you determining volume? Above you said you worked with 50 ml, but measured how? Did you use a beaker to the 50 ml line? Or a graduated cylinder to its 50 mL line?
Well i am using a 50mL beaker and a 0,00g scale to measure the weight and volume, and yes i did use and follow the 50mL line. (do you recommend a grauated cylinder more than a beaker?)
Or did you use a pycnometer, which is the only way to be truly accurate?
This goal is not get 99,99999% of the solution, but say that there is between 7-9% of alcohol in this beer, or 23-25% of ammonia in this 1L bottle
Here's an experiment for you. Determine the density of distilled water. Do it 10 times, (or 20, or 50 or 100, if you're dedicated enough.) You can determine your accuracy -- the density of water, at 25 °C (you have been controlling the temperature all along, correct? Density varies with temperature,) is defined as 0.997. How close to this number is your average of ten trials? What is your precision? That can be defined as the standard deviation (most calculators and Excel will compute that for you,) in simple terms. How good are you at getting close to the same number over multiple trials. That will tell how good any one trial of your is.
Dident had any destilled water, but gonna try to get some later today. Anyway, saw that i had a brand new fresh 5L water (think its filter water, and yeah! i know that distilled water and filter water is not same, but this was just a experiment on it, gonna try the destilled water when i got some) so i tryed to measure it 20 times, and here was the result: http://pastebin.com/2xSHGNkq - it comes between 48,14g and 48,95g on 50 ml (20-21°C), (average 48,5905g on 50 mL) My standard deviation was 0.27458.
This is what science is, and I'm saddened that no one seems to know this. Lately, particularly on this board, the definition of "fun" science is "Look at me, I can make drugs, but I'd never take them, but Whee, I'm awesome" or "Look at me, I can make the ingredients for bombs, but I'm totally not a terrrrist, but lookithow awesome I am." If you want to try to understand the anomalous results, checking your abilities is a good place to start.
Yeah, seems that science was much more tougher than i expected, but i am happy to continue learning this ;)
Now let the argument and complaining come ;D
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I think the reason you got 30% is because they use % by weight, not volume.
A 25% solution by weight has a density of 0.91 g/cm3.
% by weight means if you have 100 grams of a 25% ammonia solution, 25 grams will be NH3 and the rest is water, very simple.
But % by volume is more complicated for a dissolved gas in water, you need the density, which must be measured, not calculated.
So, 25% NH3 by weight, = 27.5 % vol, the rest is probably a measuring mistake on either your part or theirs (probably yours ;D).
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I think the reason you got 30% is because they use % by weight, not volume.
A 25% solution by weight has a density of 0.91 g/cm3.
% by weight means if you have 100 grams of a 25% ammonia solution, 25 grams will be NH3 and the rest is water, very simple.
But % by volume is more complicated for a dissolved gas in water, you need the density, which must be measured, not calculated.
So, 25% NH3 by weight, = 27.5 % vol, the rest is probably a measuring mistake on either your part or theirs (probably yours ;D).
Thanks Zyklonb, you are really into something there!
So, 25% NH3 by weight, = 27.5 % vol, the rest is probably a measuring mistake on either your part or theirs (probably yours ;D).
Yeah, i should have measure it 10 times, and then calculate the average of it.
But how did u find out 25% NH3 by weight, = 27.5 % vol?
Could you give me an example?
I got a 1L bottle of sulfuric acid, on the bottle it stand 60-100%, when i measure it with 50 mL i got 93,34g
93,34g * 2 = 186,68g
186,68g / 100 = 1,8668 g/ml density
And here is the density table for it: http://www.sschemical.com/wp-content/uploads/2013/05/Conversion_Table.pdf
The highest % here is 1,8391 g/ml but this must be calculated in volume, but how u calculate in weight?
Thanks!
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http://www.chembuddy.com/?left=concentration&right=mass-percentage
http://www.chembuddy.com/?left=concentration&right=mass-volume-percentage
http://www.chembuddy.com/?left=concentration&right=volume-volume-percentage
http://www.chembuddy.com/?left=concentration&right=wrong-percentages
and the second example in
http://www.chembuddy.com/?left=concentration&right=concentration-follies
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Thanks borek, for sending links, did get a step closer ;)
But still got stuck on the sulfuric acid, because one of the link you gave me, there we know aldready what % (80%) is in the acid. and can calculate it.
But in my example i got between 60-100%, and not a speific % :(
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I told you long ago - you either know the concentration as it was given to you, or you determine it experimentally. If you know what it is, you can convert between different units, if you don't know, no amount of calculations is going to give you an answer.
Density table you linked to contains information about w/w percentage.
The density you have measured is higher than the maximum density of the sulfuric acid solutions, most likely it means you have a systematic error and your measurements are unreliable.
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Density table you linked to contains information about w/w percentage.
The density you have measured is higher than the maximum density of the sulfuric acid solutions, most likely it means you have a systematic error and your measurements are unreliable.
Or maybe my calculation is like Zyklonb told, that i am calculating volume and not weight. + (some measuring mistake)
I think the reason you got 30% is because they use % by weight, not volume.
A 25% solution by weight has a density of 0.91 g/cm3.
% by weight means if you have 100 grams of a 25% ammonia solution, 25 grams will be NH3 and the rest is water, very simple.
But % by volume is more complicated for a dissolved gas in water, you need the density, which must be measured, not calculated.
So, 25% NH3 by weight, = 27.5 % vol, the rest is probably a measuring mistake on either your part or theirs (probably yours ;D).
when i was calculating ammonia, the % was much higher then the on the description.
maybe its same concept here with the sulfuric acid also?
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Density is mass divided by volume. You know this. But how do you get mass? And how are you determining volume? Above you said you worked with 50 ml, but measured how? Did you use a beaker to the 50 ml line? Or a graduated cylinder to its 50 mL line? Or did you use a pycnometer, which is the only way to be truly accurate?
So i was looking for a pycnometer, but then i found this https://www.youtube.com/watch?v=XgeDwl0Fq3w, can this one be more accurate? because you can measure the ml and you just need a accurate scale then you can calculate the density :)?
I don't jump right onto YouTube, because my internet pipe is too narrow. However, by the name, that doesn't look like an accurate volume measurement device exactly. Maybe you'd like to use a burette, to accurately measure volume, and then determine mass, but automatic titrators measure a particular volume at a certain chemical endpoint. Although I suppose they could be programed to dispense a certain volume. They cost thousands of dollars 'tho.
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Hello!
Let's finish this thread ;)
Anyway Arkcon, i have spend some time to try to get one pycnometer, so i got a 50ml pycnometer now.
So... Lets continue.
I got 1 Liter of H2SO4, which on the description it stand 60-100% and what i want is to try to find the specific concentration in the bottle.
So what i have done is to measure several times with a 50ml pycnometer, and a temperature meter.
50ml pyconmeter empty: 34,15g
Average 50ml pycnometer with H2SO4: 126,91g (pour in and out several times, and measure it)
Weight of the H2SO4: 92,76g
Temprature: 7,5 cel to 10,5 cel
So how do i calculate it? Tryed to use Chembuddys calculator, but gave me 185% concentration which is not possible :)
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Weight of the H2SO4: 92,76g
What is the volume? What is the density then?
Please note that you should not assume pycnometer holds exactly 50 mL, but you should calibrate it using water first.
Temprature: 7,5 cel to 10,5 cel
No idea what you mean. There should be only measurement of the temperature and I don't know what "cel" is intended to mean. Celsius degrees?
So how do i calculate it? Tryed to use Chembuddys calculator, but gave me 185% concentration which is not possible :)
Then you did something wrong. 1.85 is definitely a number that shows up during calculations, but it is not the concentration.
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Hello Borek
Volume is 50 mL and the weight of H2SO4 is 92,76g
92,76g / 50 mL = 1,8552 g/mL . But highest % of H2SO4 is 1.84 in density, so something is wrong here...
Please note that you should not assume pycnometer holds exactly 50 mL, but you should calibrate it using water first.
Arkcon : Density is mass divided by volume. You know this. But how do you get mass? And how are you determining volume? Above you said you worked with 50 ml, but measured how? Did you use a beaker to the 50 ml line? Or a graduated cylinder to its 50 mL line? Or did you use a pycnometer, which is the only way to be truly accurate?
Something i missing here?
About the : Temprature: 7,5 cel to 10,5 cel, yes i mean Celsius degree, sorry.
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So how do i calculate it? Tryed to use Chembuddys calculator, but gave me 185% concentration which is not possible :)
Then you did something wrong. 1.85 is definitely a number that shows up during calculations, but it is not the concentration.
I know i did something wrong :P Thats why i seek for some help for what am i doing wrong.
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Density depends on temperature. What is the temperature your table of sulfuric acid densities is calibrated at? Its usually closer to ambient than 7.5 to 10.5. Your temperature range is quite wide, you will have to expect deviations when your system is not as under more control. Are you sure you're using the pyconometer properly? Usually, they're calibrated at a certain temperature, again, closer to room temp 25 °C. You're supposed to fill it cold, warm it up to the calibrated temp (allowing some fluid to escape, because liquids expand when when warmed,) then clean and dry the outside rapidly. Then take the mass.
Again, repeated tests with water are important to see how precise and accurate you can be. If you can get the density of water to be 0.997, then you're doing well. If its off, you have to admit that your results for sulfuric acid are going to be off. If you're correct, but only once or twice out of twenty, then you analyze the sulfuric acid 3 times, you essentially know nothing -- you can make no predictions on your sulfuric acid density results. Again, this is what science is really about. So few people really understand that.
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Hello Arkcon
Im using these density tables:
http://www.inyoprocess.com/images/chem_appl/sulfuric%20acid%20properties.pdf
http://www.norfalco.com/EN/ProductsServices/Documents/NorFalco_H2SO4Property02.pdf
http://www.sschemical.com/wp-content/uploads/2013/05/Conversion_Table.pdf
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Something i missing here?
Pycnometer is designed to hold each time exactly the same volume of the liquid. Its volume is not given, 50 mL is just an approximation. Exact volume of each pycnometer is something you have to measure before using it. However, once you measure its volume in a given temperature, you can be sure volume stored is reproducible to a very high degree.
Please note density you got is already quite informative - you can be sure this is more or less pure acid (around 100%, perhaps just a typical 98% stock solution). Density of the 60% solution would be around 1.5 g/mL.
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Something i missing here?
Pycnometer is designed to hold each time exactly the same volume of the liquid. Its volume is not given, 50 mL is just an approximation. Exact volume of each pycnometer is something you have to measure before using it. However, once you measure its volume in a given temperature, you can be sure volume stored is reproducible to a very high degree.
Please note density you got is already quite informative - you can be sure this is more or less pure acid (around 100%, perhaps just a typical 98% stock solution). Density of the 60% solution would be around 1.5 g/mL.
Thanks!
Okay, did go to the store and bought some "battery water" for cars. It stands: demineralised water.
So what was my result?
Well, this time i had 3 - 0,01g weight.
the pycnometer weight was between 34,11g to 34,13g - 0,02g deviation between
pycnometer with destilled water was between 84,38g to 84,44g - 0,06g deviation between
the temprature was 20 degree celsius
So then the calculation will be:
84,41g - 34,12g = 50,29g water
50,29g water / 50ml = 1,0058 g/mL
So what conclusion will it be?
I also tryed this, because i know this is distilled water, and have a pycnometer, maybe something hidden or invisible dirt inside or out side the pycnometer, also i havent calibrated the scales (but had 3 of them)
But anyway, i found this site : http://antoine.frostburg.edu/chem/senese/javascript/water-density.html - and if i put 20 degree celsius on it, it cames up 0,9982.
So if i take my result:
1,0058 - 0,9982 = 0,0076 deviation.
If i take this deviation on the H2SO4 my result will be like this:
1,8552 g/mL - 0,0076 deviation = 1,8476 g/mL
Well 1,84 g/mL is 100% H2SO4, but im getting closer :)
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Hello Arkcon
Im using these density tables:
http://www.inyoprocess.com/images/chem_appl/sulfuric%20acid%20properties.pdf
http://www.norfalco.com/EN/ProductsServices/Documents/NorFalco_H2SO4Property02.pdf
http://www.sschemical.com/wp-content/uploads/2013/05/Conversion_Table.pdf
Tabl1 1 specifies 60° F, that is 16°C, you can't use a pycnometer of sulfuric acid at 10°C with that table. Likewise table 3. Table 2 can be used. Check your pycnometer with water first. If it is accurate with a few readings, fine. Otherwise keep using it properly until you can use it properly.
Since the way a pycnometer is used is to basically overfill it, and let the liquid run out an overflow as you bring it to temperature, I hope you're being very careful with conc sulfuric acid.
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50,29g water / 50ml = 1,0058 g/mL
No, that's not how you do it. You should calculate exact volume from the measured mass and density of pure water taken from the density tables.
Alternatively, you can measure the water weight, the sulfuric acid weight then divide the latter by the former. What you will get this way is called "specific gravity" and is - for most practical purposes - numerically identical with density (although it slightly differs, typically in the 0.01% range).
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Tabl1 1 specifies 60° F, that is 16°C, you can't use a pycnometer of sulfuric acid at 10°C with that table. Likewise table 3. Table 2 can be used. Check your pycnometer with water first. If it is accurate with a few readings, fine. Otherwise keep using it properly until you can use it properly.
Since the way a pycnometer is used is to basically overfill it, and let the liquid run out an overflow as you bring it to temperature, I hope you're being very careful with conc sulfuric acid.
Have tryed to fill it with water and got 1,0058 g/mL on average
It must be atleast 0,35g-0,40g missing weight ,but how is that possible? the pycnometer is filled and the fluid is running out.
50,29g water / 50ml = 1,0058 g/mL
No, that's not how you do it. You should calculate exact volume from the measured mass and density of pure water taken from the density tables.
Alternatively, you can measure the water weight, the sulfuric acid weight then divide the latter by the former. What you will get this way is called "specific gravity" and is - for most practical purposes - numerically identical with density (although it slightly differs, typically in the 0.01% range).
hmm? "You should calculate exact volume from the measured mass and density of pure water taken from the density tables."?
1,855g/ml H2SO4 / 1,0058g/ml water = 1,8443 g/mL still over 1,84 :(
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hmm? "You should calculate exact volume from the measured mass and density of pure water taken from the density tables."?
Which part you don't get? Just get the definition of the density, solve for volume, and plug your knowns.
1,855g/ml H2SO4 / 1,0058g/ml water = 1,8443 g/mL still over 1,84
What is the balance you are using, is it leveled? Are your weights calibrated? What is the balance accuracy?
Pycnometer - while not a very sophisticated device - requires a good technique to make the results reliable. For example, after filling it has to be carefully dried out on the outside. I do remember there were some small tricks we were taught, but it was 30 years ago, so I don't remember them.
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Until recently, I've been using a pycnometer almost constantly all day. And yes they are simple, if tedious, to work with. However, if you're soppy, you won't get good results. There is simply no shortcut to the tedium.
A pycnometer must be scrupulously clean. My standard method was to soak it in hot soapy water, and rinse with distilled water thoroughly, before drying the cap, and pycnometer in a 105 C oven. The thermometer can't be treated that way (I absent-mindedly tried once, sent all the mercury to the end and it never left,) but still must be cleaned and dried. The assembly is never touched, not even with gloved hands, I carry it in a folded up kimwipe as a holder. For quarterly calibration, the empty dry pycnometer is weighed in triplicate. This is, in some ways not needed, the mass is never different, not even at the 4th decimal place. But at least it establishes that the balance is reliable.
Then there's triplicate runs of distilled water. This is where simple, but tedious comes in. You fill with water, you drop the thermometer in, some overflows, but you check the temperature. You warm in your hand until almost 25 C, using a kimwipe to soak up droplets as it overflows from warming. The last mounded droplet, on the pycnometer side-arm, at exactly 25 C is removed with the corner of a kimwipe. If you suck the water out to below the side arm's level by capillary action -- screw you, start over. If its OK, put the cap on, and read the mass. In triplicate.
Here's something I observed, that you don't hear about anywhere else. The first reading is often lower than subsequent readings. I don't know why that is, perhaps the ground glass joints hold water within them? Or maybe the glass itself has microscratches that make it porous. Anyway, I always fill, set it up and then dump the water out a few times before the first mass. And of course, you don't take any sample readings without a through rinse, especially when the sample is nothing like water, for example, a solution of an emulsified fat that's meant to add viscosity to a formulation.
Trizocy:, you seem to want really good results, but you don't mention how much work you're going through to insure your accuracy and precision. You keep telling us one number, on average, but how close are your numbers to each other? How close are they to the theoretical density of water at room temperature?
P.S. of course, I neglect to mention, I also have to calibrate my pycnometer fitting thermometer to a NIST standardized thermometer. That's a little too much to expect of you Trizocy:. However, bear in mind that in my experience they always deviate -- at least by 0.5 C, sometimes as much as ±1 or 1.5 C. You can certainly check at two points -- 0 C for ice and water, and 100 C for boiling water. If the thermometer can handle boiling temps (c.f. above.)
*EDIT -- I spell better later in the day*
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You can certainly check at two points -- 0 C for ice and water, and 100 C for oiling water.
I wouldn't trust boiling without checking the pressure first.
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You can certainly check at two points -- 0 C for ice and water, and 100 C for oiling water.
I wouldn't trust boiling without checking the pressure first.
Of course, now that you mention it, we can't rely on the boiling point being a standard temperature without taking local atmospheric pressure into account. I guess I oversimplified. ;D Sorry Trizocy: see what happens when we look for shortcuts.