why does KF have a pH greater than 7 and not a pH equal to 7

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why does KF have a pH greater than 7 and not a pH equal to 7

Postby Chem_Mod » Sun Aug 21, 2011 12:00 pm

Anions of strong acids are such weak bases that they have no significant effect on the pH of a solution and are considered basic in water, why does KF have a pH greater than 7 and not a pH equal to 7? Why is the pH 7 and not above 7 for KBr?

Chem_Mod
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Re: why does KF have a pH greater than 7 and not a pH equal

Postby Chem_Mod » Sun Aug 21, 2011 12:01 pm

Because F- is the anion of a weak acid (remember that HF is NOT a strong acid like the rest of the hydrohalic acids). The conjugate base of a weak acid is in fact basic in solution, raising the pH above 7. Both HBr and KOH are strong acids and bases, respectively. Conversely, Br- and K+ must be very very weak bases. Because they are so weak their effect on the pH of a solution is negligible.


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