why are sodium bicarbonate and ammonia bases?

[Chooco]

sodium bicarbonate - NaHCO3
ammonia - NH3
ions of sodium bicarb: Na^+ H^+ CO3^2-
ions of ammonia: none, it is a molecule

most bases have hydroxide ions - OH to take the H off the acid and make water............how would sodium bicarbonate or ammonia take the extra H from the acid?

 

[Sahakiel]

Ammonia ionizes to NH4+

 

[Sukhoi]

NaHCO3 + H2O = Na + H2CO3 + OH

 

[Chooco]

i figured something out with the baking soda
NaHCO3 + HCl = NaCl + H2CO3 this equation is not balanced but you get the idea
baking soda can turn strong acids into weak acids

 

[Chooco]

<< NaHCO2 + H20 = Na + H2CO2 + OH >>


that is not baking soda

 

[Sukhoi]

Sorry, it's CO3, had a brain fart. My equation is still correct.

 

[Bremen]

Basically this goes to the question of what is an acid/base? Most people think in terms if hydrogen/hydroxide. This is an easy way to determine acid/base. However this is not the only way to define what an acid/base is. There are nice names associated with these definitions, but I do not care to recall them ;0)

Anyway, the broadest way to define acid/bases is by electron transfer. An acid is a electron reciever, while the base is the donor. In the case of hydrogen H^+ + e^- = H, normally it would bond to another molecule to get the electron (this tends to muddy the waters as to whats giving the electron). Although in reactions not taking place in water, it becomes alot easier to differentiate. For instace batteries are a acid/base reaction where the two reactants do not come into contact but still transfer electrons.

 

[Chooco]

well technically sodium bicarb and ammonia are NOT bases but they act like bases
an acid is a substance in which the amount of hydrogen ions is more than 1x10^-7, the pH is the negative log of the moles/litre. the formula for pH is: pH x pOH = 1x10^-7 meaning that when the H goes up the OH goes down. if the moles/litre of H is 3.4x10^-5 we do this:
-log(3.4x10^-5)
=4.468
pH = 4.47

an acid would not only bring the pH from a number higher than 7 to 7 but below 7, bases would bring the pH from less than 7 to greater than 7. ammonia will neutralize acid but it will not make the solution basic.

 

[Sukhoi]

<< ammonia will neutralize acid but it will not make the solution basic >>



You sure about that? Add some NaOH to NH4Cl. You get NH3 gas given off, and when it makes contact with wet hydrion (sp?) paper, it turns very basic.

 

[Chooco]

your test is flawed, the solution turns basic because you added NaOH.

 

[Sukhoi]

?? You don't put the hydrion paper in the solution! You hold it over the reaction. The NH3 given off turns the wet hydrion paper basic.

 

[Belegost]

Chooco, both ammonia and sodium bicarbonate are bases.

Bremen is right in the definition, substances that will donate an electron pair in a reaction are called Lewis bases, and those that give up an electron pair are Lewis acids. Alternatively, when dealing with liquid acid-base reactions, you can just as easily consider protons being exchanged, so the definition of a Bronsted-Lowry base is one that accepts a proton, and a Bronsted-Lowry acid is one that donates a proton.

It now becomes easy to see why ammonia and sodium bicarb are bases, in a reaction they will tend to donate an electron pair, or (saying the same thing) accept a proton.

This may also help explain why aqueous ammonia is generally labeled ammonium hydroxide (NH4OH) in the lab.

 

[joohang]

<< sodium bicarbonate - NaHCO3
ammonia - NH3
ions of sodium bicarb: Na^+ H^+ CO3^2-
ions of ammonia: none, it is a molecule >>



NH3 by itself is not a base. It forms a basic solution when it comes in contact with water. Same goes to sodium bicarb:

NH3 + H2O <-> NH4+ + OH-
NaHCO3 + H2O <-> Na+ + HCO3- <-> Na+ + H2CO3 + OH-

If I recall correctly, they are both weak bases, btw.



<< most bases have hydroxide ions - OH to take the H off the acid and make water............how would sodium bicarbonate or ammonia take the extra H from the acid? >>


Read Belegost's post.

 

[rgwalt]

Sodium Bicarb and ammonia are both bases when added to water. Ammonia will accept a proton from a water molecule to form NH4+ and an OH- ion. If you have an acidic solution and you add ammonia to it, it will neutralize the acid, and then will continue to ionize to make the solution basic.

Ryan

 

[Mday]

um

remember that what makes a substance an acid or base is somewhat dependent on the type of reaction is taking place. this is especially true under the lewis definition.

freshman chemistry tells us that there are 3 classifications of acid\base, as belegost said (he did not mention arrhenious (sp))...