Acids and bases

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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-?
 

Answers and Replies

  • #2
Borek
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NaOH in water is fully dissociated. What is a proton acceptor in this solution?
 
  • #3
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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?
 
  • #4
Borek
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You are still ignoring fact that NaOH is fully dissociated. There is no such thing as NaOH in solution, so it can't react.
 
  • #5
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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?
 
  • #6
Borek
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how if NH3 and HCl reacted? Would the result be NH4+ and OH-?
Why OH-?
 
  • #7
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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?
 
  • #8
Borek
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NH3 has a lone pair that can accomodate H+, thats right. However, where is the source of OH-? Please remember you are reacting NH3 with strong acid.
 
  • #9
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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?
 
  • #10
Borek
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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.
 
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  • #11
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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?
 
  • #12
Borek
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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.
 
  • #13
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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?
 
  • #14
Borek
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No, conjugate acid and conjuage base differ just by one proton.
 
  • #15
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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?
 
  • #16
Borek
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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.
 
  • #17
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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?
 
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  • #19
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Ok thank you very much for your help so far.
 

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