[NewtoAtoms]

Can anyone explain to me why some conjugate bases give basic solutions in water, while the aqueous solutions of other conjugate bases remain neutral?

I realize that some ions can be acidic (ie. NH4+, Al3+, Pb 2+)
as I also realize that some ions can be basic (F-, NO2-)
but then some ions can also be neutral (Na+)

can anyone explain this to me... I am a tad confused.

New to atoms

[AWK]

F^- + H2O = HF + OH^-

[NewtoAtoms]

Hello Awk,

Okay, I got your reply, thank you however I am still confused.

F- + H20 ----------> HF + OH- means that there is a hydroxide ion left over meaning that F- is a basic ion???
NH4+ + H20 -------> NH3 + H30+ means that there is a H30 left over meaning that NH4+ is an acidic ion.

But how do I explain an ion like Na+

Na+ + H20 --------> ?

I am not sure why Na+ is rated as a neutral ion.

Any help would be so wonderful!

Thank you

Newtoatoms

[Vidya]

F- + H20 ----------> HF + OH-
HF<===> H+  + F-
HF is a weak acid and responsible for taking up H+ ions from water.
[H+]<[OH-]
so solution become basic.
Na+ + H2O  --->  Na+  +   OH- + H+
But NaOH is a strong electrolyte and is completely dissociated
NaOH---->   Na+  + OH-
So  OH - are not consumed .and [H+]= [OH-]
Solution is neutral.

[Rabn]

Hi NewtoAtoms.  Are you familiar with the topic of equilibrium in the context of solutions?  Can you tell me makes an acid "strong" or "weak"? How do conjugate acids and bases relate to the acids and bases from which they originated? Are you familiar with the strong and weak acids and bases? (i.e. if I asked to give me the chemical formula for sodium hypochlorite, could you answer without looking it up?)  Answering these questions will really help us figure out what you know; that will make it easier to help you down the road.

[AWK]

F- + H20 ----------> HF + OH-
HF<===> H+  + F-
HF is a weak acid and responsible for taking up H+ ions from water.
[H+]<[OH-]
so solution become basic.
Na+ + H2O  --->  Na+  +   OH- + H+
But NaOH is a strong electrolyte and is completely dissociated
NaOH---->   Na+  + OH-
So  OH - are not consumed .and [H+]= [OH-]
Solution is neutral.

You forgot about equlibriums. Solution of NaF is sligtly basic, ie pH 0f 0.05 NaF is about 7.9

[Vidya]

In NaF, again F- is a conjugate base which can accept a proton from water to form HF. I was talking about salts like NaCl and Na2SO4. They form neutral solutions. I hope I am clear now.

[AWK]

NaCl -  I agree
Na₂SO₄ - not exactly true

[Yggdrasil]

HCl is a strong acid because it completely dissociates into H⁺ and Cl^-.  Put another way, this means that Cl^- has no tendency to bind H⁺ in solution.  Therefore, when you put chloride anions into water, the chloride will not "soak up" H⁺ in solution and make the solution basic.  In contrast, F^- is the conjugate base of a weak acid.  Because HF is a weak acid, F^- has the ability to bind to protons in solution and can thus make the solution basic.

[cliverlong]

F- + H20 ----------> HF + OH-
HF<===> H+  + F-
HF is a weak acid and responsible for taking up H+ ions from water.
[H+]<[OH-]
so solution become basic.

Sorry, I don't understand what you have written. I am seeing the words
"HF is a weak acid ... so solution become basic."
How can HF be both acidic and basic?

and you also write:
"HF is a weak acid and responsible for taking up H+ ions from water."
Surely as an acid HF provides H+ not "takes up" H+ ions.

Na+ + H2O  --->  Na+  +   OH- + H+
But NaOH is a strong electrolyte and is completely dissociated
NaOH---->   Na+  + OH-
So  OH - are not consumed .and [H+]= [OH-]
Solution is neutral.

What do you mean by "OH- are not consumed and the solution is neutral"
Aqueous NaOH is a strong alkali.

I suggest the questioner reads a clear account of acids and bases, such as:

http://www.chemguide.co.uk/physical/acideqiamenu.html

starting at the beginning.

Clive

[Vidya]

I think you must read about salts of weak acids and weak bases.

[Borek]

I think you must read about salts of weak acids and weak bases.

I think I was able to understand what you meant, but I agree with cliverlong - your post is chaotic and can be confusing, especially to someone who doesn't understand Brønsted-Lowry theory yet.

HF is a weak acid and responsible for taking up H+ ions from water.

I suppose what you mean is that F^-, as a conjugate base of weak acid, will react with H⁺ increasing solution pH. But that's not what you wrote. HF is an acid and it can only add H⁺ to solution, not remove it.