Neutralization Reactions: NaOH + HCl & NH3 + HCl

[DarylMBCP]

Homework Statement

An acid and a base is supposed to form a salt and water during a neutralization reaction such as NaOH + HCl --> NaCl + H₂O. However, based on Brønsted–Lowry acid-base theory, shouldn't NaOH become NaH₂O or something like that after accepting an H+ ion from HCl since the base is a proton acceptor? Why does the OH- ion from NaOH get separated?

My next question is...
What is the result when the base, NH₃ reacts with the acid HCl, for example? Is the result NH₄+ and Cl-?

 

[Borek]

NaOH in water is fully dissociated. What is a proton acceptor in this solution?

 

[DarylMBCP]

In Brownsted- Lowry Theory, bases are said to be proton acceptors and acids are said to be proton donors and since NaOH is a base in this solution, shouldn't it receive a H⁺ion from HCl, which is an acid? When NH₃, a base and H₂O react, NH₄⁺ and OH^- are produced. In this case, a H⁺ ion is transferred from H₂O to NH₃ whereas in the NaOH and HCl reaction, a H⁺ ion is not tranferred from the acid to the base. Why is this so? Does this have something to do with water having a unique property?

 

[Borek]

You are still ignoring fact that NaOH is fully dissociated. There is no such thing as NaOH in solution, so it can't react.

 

[DarylMBCP]

Oh ya, I completely forgot about that. Thank you. However I do have another question on how if NH3 and HCl reacted? Would the result be NH₄⁺ and OH^-? But if that is so, then it would mean that when an acid reacts with a base, a salt and water is not always the result. If so, when does this rule apply and when does a reaction between a base and an acid result in another acid and base?

 

[Borek]

how if NH3 and HCl reacted? Would the result be NH₄⁺ and OH^-?

Why OH^-?

 

[DarylMBCP]

OH^- because NH₄⁺ gains a H⁺ ion since it is the base resulting in OH^-. So are NH₄⁺ and OH^_ the products for such a reaction?

 

[Borek]

NH₃ has a lone pair that can accommodate H⁺, that's right. However, where is the source of OH^-? Please remember you are reacting NH₃ with strong acid.

 

[DarylMBCP]

remember you are reacting NH3 with strong acid

Are you referring to H₂O as the strong acid since it is left to react with NH₃?

 

[Borek]

Are you referring to H₂O as the strong acid since it is left to react with NH₃?

No, please take a look again at the original question you have posted.

how if NH3 and HCl reacted?

You listed two substances, one of them is a strong, mineral acid. One of the most common strong acids.

 

[DarylMBCP]

Sorry about that. I forgot about my original question in mind. What I mean is, I do have question on how if NH₃ and HCl reacted? Would the result be NH₄⁺ and Cl^-? But if that is so, then it would mean that when an acid reacts with a base, a salt and water is not always the result. If so, when does this rule apply and when does a reaction between a base and an acid result in another acid and base?

 

[Borek]

What I mean is, I do have question on how if NH₃ and HCl reacted? Would the result be NH₄⁺ and Cl^-?

Yes.

But if that is so, then it would mean that when an acid reacts with a base, a salt and water is not always the result. If so, when does this rule apply and when does a reaction between a base and an acid result in another acid and base?

Look for extended definitions of acids and bases. Classic one (Arrhenius) treats everything in terms of OH^- and H⁺ - it fails for ammonia and HCl reaction. This one can be easily understood in terms of Brønsted-Lowry's acids and bases.

 

[DarylMBCP]

Actually, I'm very new to the topics od Acids and Bases so I don't think I was able to understand everything on that webpage very clearly. Still, this is what I think it meant and how it applies to my question; Ammonia and HCl for NH4+ an Cl-. NH4+ is a conjugate acid and Cl- is a conjugate base. Am I right?

 

[Borek]

No, conjugate acid and conjuage base differ just by one proton.

 

[DarylMBCP]

So let me try to get what u are saying and from the hyperlink you attached; The reaction I stated above results in NH₄⁺ and Cl^- and both aren't a conjugate acid and base pair. That is because the base, NH₃ does not contain OH^-. Is that true?

 

[Borek]

NH₄⁺ and Cl^- and both aren't a conjugate acid and base pair

My English fails me here and I am not sure what you mean (word 'both' make the statement unclear for me). IF you mean that NH₄⁺ is not conjugate acid of Cl^- and vice versa - then you are right.

That is because the base, NH₃ does not contain OH^-. Is that true?

It can be put this way, but it doesn't have to. You are all the time trying to use Arrhenius definition of base to ammonia - that's why you still have problems understanding the case.

 

[DarylMBCP]

It can be put this way, but it doesn't have to. You are all the time trying to use Arrhenius definition of base to ammonia - that's why you still have problems understanding the case.

What is that other way or definition that my explanation can be put? Is it that a base is defined as any substance that can accept a hydrogen ion?

 

[Borek]

Yes, as I have already posted - you need Brønsted-Lowry's theory of acids and bases.

 

[DarylMBCP]

Ok thank you very much for your help so far.