Titration question

[lex1489]

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"A solution of NaOH and HF are titrated to the endpoint of a titration. The final solution will contain?"

Answer: H2O, H+, OH-, HF, Na+ and F-

Why doesn't all the HF dissociate in basic solution? Shouldn't all that OH- take the H's off of HF?

 

[loveoforganic]

Everything's an equilibrium. Bit of a tricky question. If you drop sodium fluoride in water, some of that fluoride is going to abstract a proton from water, forming OH-.

 

[Blarelli]

"A solution of NaOH and HF are titrated to the endpoint of a titration. The final solution will contain?"

Answer: H2O, H+, OH-, HF, Na+ and F-

Why doesn't all the HF dissociate in basic solution? Shouldn't all that OH- take the H's off of HF?

F- is a decent base. It'll take a hydrogen off of a water molecule.

 

[lex1489]

Would this be the case for any weak acid (or weak base for that matter)-- that regardless of how much strong base (or strong acid for the weak base) is added, some acid (base) will always remain? That it will never dissociate completely?

 

[iamgosu]

Would this be the case for any weak acid (or weak base for that matter)-- that regardless of how much strong base (or strong acid for the weak base) is added, some acid (base) will always remain? That it will never dissociate completely?

yep...weak acids/bases don't dissociate completely.

 

[chromosome21]

yep...weak acids/bases don't dissociate completely.

true, and all salts can dissociate completely in water. If it were NaF, then Na+ and F- would have dissociated completely.

 

[loveoforganic]

what do you mean all salts can dissociate completely?

 

[iamgosu]

what do you mean all salts can dissociate completely?

assuming solution is not saturated (or supersaturated), most salts are 100% soluble in water, so it breaks down into its respective cations and anions.

obviously there's some insoluble salts though, like AgCl and BaSO4

 

[loveoforganic]

I think it's quite a stretch to say most salts are 100% soluble in water, especially since 100% soluble doesn't have much meaning, but yeah.

 

[luv8724]

Yeah.. considering the fact that HF is a weak acid.. its conjugate must be not strong but somewhat decent... so it will definitely attract proton from the water...

 

[iamgosu]

I think it's quite a stretch to say most salts are 100% soluble in water, especially since 100% soluble doesn't have much meaning, but yeah.

arbitrary number 😀