Japanese firebelly escaping and not eating

[jesper]

"All of the units including molarity is a fraction"

No, that is not true. Mol per liter is not a fraction.... Avagadros constant 6,02*10^23 tells us how many atoms that fit into one mol. Avagadros constant is defined as the number of carbon atoms with a mass of 12 g.
That is one mol of a substance is equivalent to 6,02*10^23 atoms of that kind - mol/l = amount/volume.

Maybe I didn't express myself very good, what I meant with a fraction was volume/volume or mass/mass or mol/mol. Those kinds of "units" ends up with no unit only a fraction, that was my point(ppm is a fraction not a unit...).

Thanks for tip on nitrospira, I have only bought bacteria cultures once when I was in a hurry getting a tank going. Surely it will be easy to prove that they don't work - add ammonia to the culture check how much is converted to nitrates...
Anyway, I wouldn't be very surprised if they don't work, it seems to be like that pretty often in the world of aquariums...

 

[edward]

Hi Jesper,
I see what you mean now. I can accept your definiton here with no problem. Old conventions do not always follow logic and are not often easy to correct.

(But we need to remember avogadros constant is an artificial ideal average as the weight of this many actual carbon atoms can be more or less than 12 grams depending upon the isotope make up of the sample.)

Even with the ammonia test it would be hard to prove/disprove the effectiveness of those cultures as you would need sterile conditions as these bacteria will colonize aquatic situations on their own.

Talk to you later.

Ed

 

[jesper]

Hi Ed,
I do not know how they defined Avagadros constant exactly, but since they nailed it down to 6,022136736*10^23 molecules per 12,0000000 gram of carbon atoms I suppose they didn't just throw in any carbon. I am pretty sure they were smart enough to use pure 12C otherwise Avagadros number would be very unscientific, not that it would matter since it is a definition and doesn't really "need" to be very logical. How logical is it to measure everything by how many atoms there are in 12 gram of carbon? Hell, at least it is more logical than most definitions around

 

[edward]

Hi Jesper,
Avogadro first published the constant in 1811, but it was not generally accepted until 1858 when Cannizzaro developed a system of atomic weights around it.
It was originally part of Avogadro's law which was derived for gases and not for C12 so that the volume of one mol of a gas at standard, temperature and pressure is 22.4 liters (If I remember correctly)(Avogadro's Law).
I'm not sure when carbon entered as part of the definiton except in the manner in which the number is applied to atomic or molecular weights.
However given when the theory was originally published it had to be an average of the isotopes available in that location.
I suspect this has been modified to "fit" convient usages for the modern chemist.

Ed

 

[jessica]

I just want to say thanks to Ed and Jesper for sharing the information you both know, and although there is quite a lot I don't know/understand, there is so much to be learned from it. Plus it's kind of fun to see well thought out "arguments"/discussions.

 

[jesper]

Yeah, I've read about that in chem class Ed - never got the hang of the different definitions there.

Most of the time you are taught the definition as how many atoms there are in 12 grams of carbon.
But as you point out if you heat carbon to a gaseous state(ooooh warm...difficult...) 22,4 l (at the standard state..)of it should weigh 12 grams. Hmmm, thats very strange cause that means that the 12 grams are not the definition.....Thanks to all my teachers for miseducating me....

I wonder what gas avagadro started out with?
The definition should be the weight of the first gas that he used I suppose? H2 maybe? Not very stable but hell..
Then the definition would be how many molecules reside in 1 gram of hydrogen gas. Equally logical...

Anyway...the original def. probably contained different isotopes but hopefully it has been corrected since.

Btw the two last number was bogus it should be:
6,0221367*10^23.

Thanx Jess, most people just think we are soooo boring

(Message edited by jesper on March 30, 2004)

 

[edward]

Hi Jessica,
Thanks for the compliment. Most people just get tired of the geek talk as we haven't mentioned newts for a couple of posts.

Hi Jesper,
Chemists are known for reassigning definitions to make it "easier" to use in calculations. Just like how the definition of atomic weight used to be for oxygen but now is set so that it makes Carbon weigh 12.000 grams.

Ahhh, but if you heat carbon to the point it is a gas you are no longer at Standard Temperature (as carbon's melting and vaporization temperature is much higher). This is why I said I wasn't sure when carbon was added to the mix. Probably around time they changed from oxygen to carbon in the late 1960s or so in dealing with atomic weights.

In case you haven't noticed yet but most of the chemistry you are taught in school is modeled on the behavior of the hydrogen atom. (this is particuarly true for the various electron "orbit" potentials that can be formed as hydrogen gives the simplest mathmatical model that seems to work. I'm going back in my memories about 20 years now so it isn't as clear as it used to be).

I thought I had read somewhere that they had added a couple of more significiant digits to the constant but never had enough interest to look up the changes.

Ed

 

[jesper]

Hi Ed,
"But as you point out if you heat carbon to a gaseous state(ooooh warm...difficult...) 22,4 l (at the standard state..)of it should weigh 12 grams."

I have absolutely no comments to my own thinking lol.... "heat carbon to gaseous state" followed by "in standard state" I have absolutely NO comments at all to that.

Anyway I'll have to check how the transition from gas was achieved. Maybe this summer

Can it be so that they just shift the "standard state" up, thus changing the volume....
That way you can choose a pressure and temp. that suits most materials(ie they are in their gaseous state), shouldn't that be possible?

 

[edward]

Hi Jesper,
Okay no comments.

But S.T.P. is rigidly defined with specific criteria so that anything that changes one of these numbers changes the others. Otherwise all of those nice laws and formula that ended up providing us with PV=nRT would not be so simple.

Given your interest in planted systems have you read Ecology of the Planted Aquarium (1999, Echinodorous Press)?

Ed

 

[jesper]

Hi,
No, I meant just changing pressure and temp for that particular experiment. The laws aren't based on the standard state, they were just chosen because they are convenient. I wouldn't want to change the standard state, that would mean a lifetime of recalculations lol.

Nah, special literature is not very easily accessible in a small market such as Sweden. I'd probably have to order it and importing one item isn't very good for the wallet.



(Message edited by jesper on March 30, 2004)

 

[jessica]

Well believe it or not I think it was a discussion between you two, Jesper and Ed, that I was able to understand more about water "hardness". I know Ed helped me a little with that once but I was still a little foggy. I learned a lot more about using distilled water to "soften" the water. I was just afraid the distilled water would be so bad, worrying it would do more harm than good. I know harder and softer aren't the best terms, but I'm trying to keep it simple for myself. Don't worry I'm not only using the distilled water, I've barely used it yet as I need to test for general hardness and I've been a lit bit of a slacker on that test. I also know you are supposed to use it with the other "harder" water.

I'm not sure how old the posts were sometimes I just sit and read for hours and get back into some from last year, so I may be wrong about who was taking part in the discussion.

Eh, that's ok if some people think it's boring. There's probably a large amount of it I won't understand unless I took some chem classes, but like I said there's always something to be learned