About Sodium Carbonate(Definition of base)

[abcd8989]

A base is a chemical which reacts with an acid forming water and salt only.
Is this definition of base true?
If true, metal carbonates are not considered as base (carbon dioxide is also formed during neutralization which violates the definition). Hence, the solution of metal carbonates are not considered to be alkalis (since alkali is a subset of base). However, metal carbonates are usually basic, e.g. sodium carbonate. I am bewildered whether we can call sodium carbonate a base then.
Moreover, I would like to know the chemical reaction of sodium carbonate representing the production of OH- ions. Thanks very much.

 

[alxm]

A base is a chemical which reacts with an acid forming water and salt only.
Is this definition of base true?

Arrhenius base: A substance which increases the amount of hydroxide ions when added to an aqueous solution.
Brønsted-Lowry base: A substance which can act as a proton acceptor.
Lewis base: An electron-pair donor.

Those are the most common, and the Brønsted-Lowry is probably the most used and the one implied by 'base' in general.

 

[abcd8989]

Arrhenius base: A substance which increases the amount of hydroxide ions when added to an aqueous solution.
Brønsted-Lowry base: A substance which can act as a proton acceptor.
Lewis base: An electron-pair donor.

Those are the most common, and the Brønsted-Lowry is probably the most used and the one implied by 'base' in general.

So, is sodium carbonate considered a base?

 

[Bohrok]

So, is sodium carbonate considered a base?

It's a Brønsted-Lowry base.

 

[Trooper100]

I find that definition true. There's really nothing complicated or more in-depth from the question. Bases are involved in neutralization reactions, which does product water and salt.

 

[Borek]

I find that definition true. There's really nothing complicated or more in-depth from the question. Bases are involved in neutralization reactions, which does product water and salt.

So, how do you explain high pH of solution of ammonia, or of solution of carbonate, or of solution of phosphate?

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[Acut]

Well, all follows from the definition of base we're using. Sodium carbonate isn't a Arrhenius base, but it is a Bronsted-Lowry.

@Borek: I agree with Trooper100. Low pH of ammonia solution can be explained since NH₃ acts as a proton acceptor. Low pH of phosphate and carbonate solutions are explained by the hydrolysis of the phosphate and carbonate ions.

 

[Borek]

I agree with Trooper100.

I can be misreading something, but Trooper has just confirmed initial definition from the very first post:

base is a chemical which reacts with an acid forming water and salt only

Now combining it with your post:

Low pH of ammonia solution can be explained since NH₃ acts as a proton acceptor. Low pH of phosphate and carbonate solutions are explained by the hydrolysis of the phosphate and carbonate ions.

Basically you have stated "base is a chemical that reacts with acid forming water and salt, but ammonia solutions are basic because ammonia reacts with water". Second part of what you stated can be not explained using definition you have listed first.

It is not that Arrhenius definition is incorrect, it is just limited and original question can be not answered using it.

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