carbonates

[akcapr]

how the heck are carbonates basic? sounds dumb but yah, wheres the OH, hows it made?

[rthmjohn]

I believe carbonates are weak bases in solution. This is because the carbonate ion itself has a -2 charge. When it dissociates in aqueous solution, it undergoes the following reaction: CO3(2-) + H2O --> HCO3- + OH - Carbonates are merely weak bases because most of the carbonate ions remain as carbonate and only few form bicarbonate (HCO3-) and hydroxide.

[The Thing]

The Arrhenius acids and bases are those chemicals that ionize into H+ and OH-, respectively. However, not all bases have to contain the OH- radical according Bronsted-Lowry explanations of acids and bases. The Bronsted-Lowry defines an acid as a proton (H+) donor and a base a proton acceptor. Mark that the "donor" actually has its proton taken away with energy, not given away. According to Bronsted-Lowry theory, when HCl reacts with water, the H2O is a base as well.

[Primarygun]

CO3(2-) + H2O --> HCO3- + OH -

Can we say that in another way?Carbonate combines with one H+ to hydrogencarbonate.

Why don't we use this perception?

[latentheat]

Carbonates get the pH high enough that you get the slippery feel on your hand.

 

Does anyone know exactly how high the pH can be raised with carbonates?

[jsatan]

I know it can be around 12.5 with sodium carbonate, I think.

Hummm.

[budullewraagh]

just a note, akcapr- for something to be a base it doesn't have to be or yield a hydroxide. it just has to be an electron donor.

 

lithium is a base.

 

lithium nitride is a base.

 

amines are bases.

 

ammonia is a base, and last i checked ammonium hydroxide did NOT exist

 

HPO4- is a stronger base than OH-

 

H3CO- is a stronger base than OH-

 

in acidic solution, CN-, for example, can be a base

[j_p]

Ammonium hydroxide doesn't exit?

[5614]

Then what are these sites talking about??

 

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

http://avogadro.chem.iastate.edu/CHEM211L/MSDS/AmmoniumHydroxide.htm

http://ptcl.chem.ox.ac.uk/MSDS/AM/ammonium_hydroxide.html

 

They're all generaly reliable sites (so wiki has the if side, but it's rarely wrong).

[jdurg]

just a note, akcapr- for something to be a base it doesn't have to be or yield a hydroxide.

 

That all depends on your definition of a 'base'. Just like most things in chemistry, there are multiple definitions that need to be kept in mind when saying something. Saying something is a 'base' is like saying something is 'reactive'. You need to specify your definitions when making the classification.

[jdurg]

Ammonium hydroxide doesn't exit?

 

If you go by the literal definition, then no, ammonium hydroxide doesn't exist. When ammonia gas is placed into water, you get NH4+ ions and OH- ions along with aqueous NH3. However, if you evaporate the water again you don't get NH4OH left over. The NH3 leaves solution and you just get water. Inside the water, you don't have the NH4+ and OH- ions forming dissolved NH4OH as a stable species. Instead the NH4+ will donate a proton to the OH- ions giving you water and ammonia gas again. So by saying that NH4OH doesn't exist isn't saying that adding ammonia to water doesn't make a basic solution. It's just saying that when you add ammonia to water, you don't get NH4+ ions, OH- ions, and the NH4OH species floating around.

 

The proper equation would be:

 

NH3 + H2O <=> NH4+ + OH-

[j_p]

Oh, right; I remember. It's just that I was using a solution last night, and, well, you confused me. But you're talking STP; now I curious, what happens under pressure?

[akcapr]

interesting . thx

[rthmjohn]

On the topic of Arrhenius and Bronsted acids and bases, are fatty acids clasified as Arrhenius or Bronsted?