Sulfuric acid in ppm

[wqchemist7501]

I was asked to make a 1000ppm sulfuric acid. I have never encountered anyone asking for ppm concentration of an acid before, at least in my field. I have 1N and 12N concentrated h2so4 in stock. How do I make this?

[Sensei]

Sounds like homework.

 

Do you know what does mean "ppm"?

 

Any scientist and student should know how to calculate ppm to moles and grams..

[John Cuthber]

In fairness, the question is so ambiguous that I rather hope it isn't homework.

I am a scientist and I couldn't give a definitive answer so I'd love to see how Sensei thinks he can.

 

Over to you...

[Sensei]

In fairness, the question is so ambiguous that I rather hope it isn't homework.

I am a scientist and I couldn't give a definitive answer so I'd love to see how Sensei thinks he can.

 

Over to you...

 

1000 ppm (parts per million=particles=molecules in this case) of H₂SO₄ means that there is 999000 ppm H₂O.

 

H₂SO₄ has mass ~98.078 u.

H₂O has mass ~18.015 u.

1 u = 1 g / N_A = 1 g/6.022141*10²³ = ~ 1.66*10^-24 g (atomic mass unit)

1000 * 98.078 u + 999000 * 18.015 u = 18095063 u. Mass of 1 million molecules solution.

If we divide 98078 u/18095063 u, we will have normal mass fraction.

 

Edited January 28, 2015 by Sensei

[John Cuthber]

Or, do I take 1 gram of acid and dilute it with a million grams of water, or do I take a millilitre of acid and dilute it with a million millilitres of water?

Unless you are dealing with gases the mass/volume interpretation is probably most common and you are wrong.

 

If you worked here

http://www.romil.com/pag_mono.htm

they would tell you that you said "it's easy" then came up with a complicated spreadsheet that gave the wrong answer.

 

The point remains- the question is ambiguous.

[Sensei]

Or, do I take 1 gram of acid and dilute it with a million grams of water, or do I take a millilitre of acid and dilute it with a million millilitres of water?

Unless you are dealing with gases the mass/volume interpretation is probably most common and you are wrong.

 

You're wrong even with your example.

If you dilute 1 gram of substance with 1 million grams of water you won't have 1 ppm (by mass), but less 1/1,000,001.. You need to dilute with 999,999 to have right proportions.

Similarly if you dilute m₁=1000 grams with m₂=1,000,000 grams, m₁+m₂=1,001,000 grams. m₁/(m₁+m₂) - concentration of first substance, m₂/(m₁+m₂) - concentration of 2nd substance.

If you're calculating concentration by using m₁/m₂, you would not even pass exam in our high school.

 

On my language wikipedia page of ppm, there is said (google translator used):

"ppm (parts per million) - way of expressing the concentration of a very dilute solutions of chemical compounds. This concentration is derived from the mole fraction and determines how much chemical compound per 1 million molecules of the solution."

"The unit ppm is also sometimes used as a way to express a fraction of the weight, but usually only in this case specifically inform the writing eg. ppm (by weight). When the abbreviation ppm does not have any additional information to the contrary, that we are talking about the mole fraction."

Edited January 28, 2015 by Sensei

[John Cuthber]

I'm sure it's someone's "law" that, when you correct something on the internet you add mistakes of your own.

We have two examples here. I said

"take 1 gram of acid and dilute it with a million grams of water"

When I meant

"take 1 gram of acid and dilute it to a million grams with water"

 

Well, OK, it's wrong- but it was early in the morning, and I had a bus to catch.

 

I don't know what your first language is,but this page is in English.

And current English usage is decisively ambiguous.

For mixtures of gases ppm usually refers to mole fraction- but that's because it's (practically) the same as volume fraction.

For solutions it's as often a "shorthand" for mass of solid dissolved in a volume of solvent that would have 999999 times that mass, if the solvent were water.

So, if I dissolve 1 mg of sugar in 1 ml of alcohol it's a 1000 ppm solution.

(i.e. it is micrograms per ml).

 

Have fun with your spreadsheet.

Perhaps the most important point is that the person who asked the question at the start of the thread can't expect a valid answer.

He needs to check with whoever asked him to make up the solution (unless he can be sure from the context that it doesn't matter (for example, if he's just washing glassware with it.).)

 

So, your spreadsheet is either exactly right or roughly 2 million times more wrong than I was, or something else.

.

Edited January 28, 2015 by John Cuthber

[Sensei]

So, your spreadsheet is either exactly right or roughly 2 million times more wrong than I was, or something else..

 

1000 ppm (per molecules) is 0.542% (per mass) which is 5420 ppm (per mass). Which is all already in SpreadSheet.

So disagreement between one method over other is 5.42 times (with 1000 ppm (per mass)).

1000 ppm (per volume) is 0.1% (per volume) (with density p=1.84 g/cm³) which is 1838.4557 ppm (per mass).

 

Look. I am not wrong, and you're not just right. We're just differently interpreting lack of information in brackets after ppm.

We are obviously agreeing on how to interpret:

ppm (per mass)

and

ppm (per volume)

We are simply disagreeing on interpretation how to proceed when there is just "ppm" alone.

 

ps. I am doing quantum physics. We do care about precise calculations..

Application visible on screen-shot is made by me. It has database of the all isotopes (3142), database of the all elements, and database of thousands of chemical compounds.

If we multiply isotope mass (from mass spectrometer) by natural abundance, repeat and add all other isotopes of same element we have average mass of element.

Then when we split chemical compound to elements, look up database for masses of elements, and add them together, we have mass of compound. Calculated. So compound doesn't have to be in database and right mass will appear. This application does it in real-time while entering data..

Edited January 29, 2015 by Sensei

[John Cuthber]

" I am doing quantum physics. We do care about precise calculations.."

LOL

http://en.wikipedia.org/wiki/Uncertainty_principle

You can calculate as accurately as you like- but the real values are uncertain.

 

 

The commercial packages for calculating masses for chemical compounds let you choose which average you want.

The really good ones don't give the spurious accuracy that yours does.

The molar mass of sulphur depends on where you get it from

http://www.chem.qmul.ac.uk/iupac/AtWt/

so your application claims an unrealistic accuracy. There's simply not enough information to state the molar mass of the sulphuric acid to that precision.

Were you not aware of this?

Shouldn't you have found out before writing an app that misleads people?

 

My method for making up a 1 ppm solution actually gave an answer that's a bit low. it gives

0.999999000000999999000000999999 ppm (m/m)

Your method gives about 5.4 ppm (m/m)

I'd say you are a lot further from what the OP wanted than I was.

 

Also, if you care about precise calculations, you are in trouble here.

Adding 1 ml of sulphuric acid to 1 ml of water doesn't give you 2 ml of mixture.

http://www.everyscience.com/Chemistry/Physical/Mixtures/a.1265.php

That's before we get to the question of how you measure a volume to a precision of a part in a million or so (unless you can do that there's no practical difference between adding 1000000 parts of water or adding 999999 parts)

 

Also, can I ask how you you would actually make up a solution- say 1000 ppm m/v of sulphuric acid to such accuracy that it would be possible to distinguish between 1 in a million and 1 in 999999?

The first step is to get the acid pure enough that you can guarantee that you know how much acid you have to that accuracy.

Good luck.

 

 

Anyway, it's good to see that you have realised that your first post here was wrong.

You said "Any scientist and student should know how to calculate ppm to moles and grams."

And it's clear that no scientist could do that (from the information available)

And it seems that you agree with my first post which said "I am a scientist and I couldn't give a definitive answer"

 

Edited January 29, 2015 by John Cuthber

[Sensei]

" I am doing quantum physics. We do care about precise calculations.."

LOL

http://en.wikipedia.org/wiki/Uncertainty_principle

You can calculate as accurately as you like- but the real values are uncertain.

That's completely different level of accuracy than we're talking about..

Difference at 3rd digit after fraction dot in atomic mass unit i.e. 1.0078 is equal to +- 0.931 MeV, nearly two masses of electron!

Difference at 5th digit after fraction dot in atomic mass unit is equal to +- 10 keV.

 

The commercial packages for calculating masses for chemical compounds let you choose which average you want.

The really good ones don't give the spurious accuracy that yours does.

The molar mass of sulphur depends on where you get it from

I told it once. Repeating myself: from mass spectrometry..

 

http://www.chem.qmul.ac.uk/iupac/AtWt/

so your application claims an unrealistic accuracy. There's simply not enough information to state the molar mass of the sulphuric acid to that precision.

Were you not aware of this?

Shouldn't you have found out before writing an app that misleads people?

 

Nonsense.

 

Ask Swansont how mass spectrometry works.

 

Masses obtained from mass spectrometry for different isotopes are quite accurate.

Your comment is equal to claiming that databases of isotopes f.e.

http://en.wikipedia.org/wiki/Isotopes_of_sulfur

contain totally wrong data.

 

 

Sulfur-32 31.97207100(15)

Sulfur-33 32.97145876(15)

Sulfur-34 33.96786690(12)

Sulfur-36 35.96708076(20)

Do you see brackets? That's what is uncertain.. Just two last digits prior bracket. That's +- few electron volts uncertain. Nowhere near +-10 keV nor +-931 keV like with 5th and 3rd digits wrong..

 

See how wrong is website link you gave:

"1 H hydrogen min 1.00784 max 1.00811"

 

1.00784 * 931.494061 MeV = 938.7969744382 MeV

1.00811 * 931.494061 MeV = 939.0484778347 MeV

 

What a garbage! Nearly 14 keV difference from real value!

 

We know that Hydrogen-1 has mass-energy approximately:

938.272046 MeV + 0.5109989 MeV - 13.6 eV = 938.7830313 MeV

 

938.7830313 MeV / 931.494061 MeV = 1.0078250314 u

 

What is isotope mass of Hydrogen-1 http://en.wikipedia.org/wiki/Isotopes_of_hydrogen ?

1.00782503207(10)

 

That's precise answer to 9 digits after fraction dot..

 

When we will include also Deuterium mass:

1.0078250321 * 0.999885 = 1.0077091322

2.0141017778 * 0.000115 = 0.0002316217

 

1.0077091322 + 0.0002316217 = 1.0079407539 u

That's quite good calculated average mass of Hydrogen.

 

Rounding it to 1.008 u causes giant 56 keV difference.

56 keV * 6.022141*10^23 = 5.4 GJ of energy (that's wrong)

(in 1 mole of Hydrogen)

Edited January 29, 2015 by Sensei

[John Cuthber]

Thanks for making it abundantly clear that you don't understand the reference I cited.

 

While I could ask Swansont, on the grounds that he's a mass spectroscopist, it would seem redundant. I am also a mass spectroscopist (at least occasionally).

 

 

Would you like to think about it some more?

I assure you that the table of data I gave is correct.

Here's a hint- do you think that the acid the original poster is asking about only contains one isotope of sulphur?

[Sensei]

Here's a hint- do you think that the acid the original poster is asking about only contains one isotope of sulphur?

 

Who said about ONE ISOTOPE?

Not me.

"If we multiply isotope mass (from mass spectrometer) by natural abundance, repeat and add all other isotopes of same element we have average mass of element."

[wqchemist7501]

thank you Sensei and John for the lively debate. I figured out that 1000ppm of sulfuric acid (h2so4) is 0.02N.

[John Cuthber]

 

Who said about ONE ISOTOPE?

Not me.

"If we multiply isotope mass (from mass spectrometer) by natural abundance, repeat and add all other isotopes of same element we have average mass of element."

Yes, you said about one isotope.

e.g. "Sulfur-32 31.97207100(15)"

etc.

But it's still progress!

Now, all you need to do is think about this " natural abundance"

and you will see why the table I cited earlier is correct (rather than "nonsense" or "What a garbage!") and why you can't state the molecular weight of his sulphuric acid to 6 figures.

Edited January 29, 2015 by John Cuthber

[Sensei]

Yes, you said about one isotope.

e.g. "Sulfur-32 31.97207100(15)"

etc.

But it's still progress!

In post I wrote about all 4 Sulfur stable isotopes:

 

"Sulfur-32 31.97207100(15)

Sulfur-33 32.97145876(15)

Sulfur-34 33.96786690(12)

Sulfur-36 35.96708076(20)"

 

Now, all you need to do is think about this " natural abundance"

I did this with Hydrogen and Deuterium, as an example. Just to show procedure..

 

For Sulfur it will be:

31.972071 * 0.9493 = 30.3510870003

32.97145876 * 0.0076 = 0.2505830866

33.9678669 * 0.0429 = 1.45722149

35.96708076 * 2.00E-004 = 0.0071934162

 

Summed together gives average 32.066084993

 

 

Your website gives: 32.06

Second entry: " 16 S sulfur 32.059 32.076"

 

and you will see why the table I cited earlier is correct (rather than "nonsense" or "What a garbage!") and why you can't state the molecular weight of his sulphuric acid to 6 figures.

We're calculating average mass of molecule.

 

In extremities of course we can take f.e.

for minimum:

 

Hydrogen-1 * 2

Sulfur-32 * 1

Oxygen-16 * 4

 

and receive mass 97.9673795424 u

 

for maximum:

 

Deuterium * 2 (or even unstable 12.32 y half-life Tritium)

Sulfur-36 * 1

Oxygen-18 * 4

 

and receive mass 111.9919283156 u

 

But it won't be average anymore. Just boundary theoretically possible (especially for rare D,S-36 and O-18)

 

For sulfuric acid there is calculated average mass 98.078. I don't think so it's wrong result.

 

See this.

http://pubchem.ncbi.nlm.nih.gov/compound/sulfuric_acid#section=Create-Date

They used the same algorithm of calculation of minimum mass (exact mass row) as I above.

And got 97.96738 g/mol

Edited January 31, 2015 by Sensei

[John Cuthber]

Have you noticed how few digits there are in some of these numbers?

"31.972071 * 0.9493 = 30.3510870003

32.97145876 * 0.0076 = 0.2505830866
33.9678669 * 0.0429 = 1.45722149
35.96708076 * 2.00E-004 = 0.0071934162"

 

Do you think there might be a reason for that?

Do you think that all samples of sulphur contain exactly 94.93% of the light isotope?

Do you realise that variations in the natural abundances of isotopes will change the measured mass- and would change how much sulphuric acid you would need to weigh out to make a 1 ppm solution to such a precision that it matters whether you add 999999 or 1000000 parts of water ?

 

Did you really think that I'd be getting it wrong all this time?

 

 

See fig 1.3 here

http://dge.stanford.edu/SCOPE/SCOPE_43/SCOPE_43_1_Chp1.pdf

[Sensei]

Did you really think that I'd be getting it wrong all this time?

Yes, I do.

 

In thread that I started 1.5 years ago about "role of isotopes in chemistry", you was the first one to write that there is no significant differences in chemical properties in compounds with different isotopes except heavy water's deuterium. Forgot your statement or learned something new.. ?

http://www.scienceforums.net/topic/79556-role-of-isotopes-in-chemistry/#entry774048

 

While it's plainly not true. Chemical compound with different isotope will have different density, different boiling points, different melting points, different speed of sound in material etc. etc. All these things are more or less related to slightly different mass of isotope.

 

After using average masses, we have average properties like in experiments and literature. After changing isotope to different, properties also change.

 

See fig 1.3 here

http://dge.stanford.edu/SCOPE/SCOPE_43/SCOPE_43_1_Chp1.pdf

On purpose of this thread you learned that apparently there are differences between S-32 and S-34 so they will be differently behaving in examples given in above PDF..

Difference like between night and day, from your older October 2013 statement.

Edited February 1, 2015 by Sensei

[John Cuthber]

Yes, I do.

 

In thread that I started 1.5 years ago about "role of isotopes in chemistry", you was the first one to write that there is no significant differences in chemical properties in compounds with different isotopes except heavy water's deuterium. Forgot your statement or learned something new.. ?

http://www.scienceforums.net/topic/79556-role-of-isotopes-in-chemistry/#entry774048

 

I remember the statement; it seems you can't, or you didn't understand it.

Here's what I actually said

in response to the assertion that only the properties of hydrogen are different between different isotopes

"Only hydrogen isotopes have different chemical properties,"

Not quite true

http://www.tandfonli...64#.Umlk__n_kao

But the differences are usually only laboratory curiosities, rather than practically useful."

The first thing I said was

" I can't think of any applications of stable isotope substituted chemicals outside the laboratory, but that isn't because we don't know about them, it's because they are not very different from the ordinary versions and they are much more expensive."

So, the first thing I did was point out that they were different- not not very different (apart from the price).

The second thing I said was to point out that the differences are not only observed for hydrogen.

 

 

So, lets be clear about this

In the thread you cited I said that there are differences between the chemical properties of isotopes: I said it twice.

 

 

In this thread, I pointed out that not all samples of an element will contain the same ratios of isotopes.

That's because they have slightly different properties- as I had said a year and a half ago.

 

Why do you think there is a "Difference like between night and day" between saying

the different isotopes are different

and

the different isotopes are different?

 

Anyway, would you please let me know the answer to the question I asked earlier.

Here it is again to help you:

how you you would actually make up a solution- say 1000 ppm m/v of sulphuric acid to such accuracy that it would be possible to distinguish between 1 in a million and 1 in 999999?