I need to understand chemical formulas that have a dot in them. For example, a "normal" looking formula is Na2CO3 which is Sodium Carbonate. However what is the deal with Sodium Percarbonate 2Na2CO3·3(H2O2) ? See the dot in there and also the 2 and the 3 before the two parts? All I have learned about so far is ionic and covalent bonds. Is this some other kind?

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Hydrated. Doesn't mean that it's wet. To remove all moisture from some chemicals requires extraordinary measures. If what you're doing doesn't require exact weight of chemical or absolute purity then you can use it, no problem. Most of the time it is inconsequential.

The anhydrous version wont have the H2O. Usually costs more, too. And it's a ***** to keep it dry. You can buy for example, anhydrous ethanol but once you pop the top it's like it sucks moisture out of the atmosphere. In next to no time you'll have 98% ethanol.

si, to second what bot said..

I knew chemistry was useful

the 2 before the sodium basically means two sodiums and Percarbonate is the proper terminology for such


what chemistry are you taking

I am taking 129 I think. It is suposed to be easy but some teachers make the difficult easy and some make the easy difficult and I have the second kind.

Anyway, this is the stuff in Oxiclean and according to some authorities it is technically a perhydrate. What I can gather is that this means the H20 has been replaced with H2O2. So that basically goes along with what Bot said I think.

Oxiclean actually has this stuff and also just some Sodium Carbonbate. When you add water you get oxygen gas (I think) and H2O2 (I think) and more Na2CO3 (I think). So if I understand, the dot means it has or had some H2O attached to it? And then it became a perhydrate when that got replaced with H2O2?

And what I really need to know is how does bleach, this kind or the regular kind, break up stains, and what does that have to do with oxidizing? And it turns out that oxidizing actually has nothing necessarily to do with oxygen but can involve any halogen? Oh my....

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

By golly, I missed he peroxide thing. My bad -- I read it as H2O.

But the same thing stands, essentially.

The H2O2 is adhered to the sodium molecule. Added to water, the H2O2 dissociates forming hydrous H2O2 and the Na2CO3 dissolves forming 2Na+ and --CO3. All of this is aqueous which means other species form temporarily and in equilibrium (IIRC).

You get: (+H) + (H2O-) + (2Na+) + (--CO3) Charges balance but I think it'll be on the acidic side. Now depending on what this solution is exposed to it's going to react. If it comes in contact with something acidic (say, iron oxide) then the sodium is going to snap it up displacing the iron and freeing CO2 + O- which will snap-up the H+ and excess iron will precipitate as reduced iron (Fe2(OH)3 (?). At a guess. A black residue.

If it is put on something with a pH above 7 then you'll get a reaction from the peroxide.

Does that sound right? Hell, it's only been 25 years.

B