Salt hydrolysis (Acid-base problem)

[Amorphisgirl]

Would anyone here know a way to remember the rules for telling whether the solution produced from the hydrolysis of a salt is acidic or basic based on ions produced. Or, am I missing the point entirely? If there is just one strong acid ion product, will the solution be acidic? If there is just one strong base ion product will the solution be basic? Thanks.

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[aye]

Would anyone here know a way to remember the rules for telling whether the solution produced from the hydrolysis of a salt is acidic or basic based on ions produced. Or, am I missing the point entirely? If there is just one strong acid ion product, will the solution be acidic? If there is just one strong base ion product will the solution be basic? Thanks.

Yup... you got it right. Try to think of it as a fight (a typical guy analogy). if a strong ion (acid or base) is w/ a weak or neutral ion, then the strong one wins and makes the solution (acidic or basic). also remember that acids and bases don't necessarily have to Bronsted Lowry, they can be Lewis acids/bases.

 

[chopper]

Would anyone here know a way to remember the rules for telling whether the solution produced from the hydrolysis of a salt is acidic or basic based on ions produced. Or, am I missing the point entirely? If there is just one strong acid ion product, will the solution be acidic? If there is just one strong base ion product will the solution be basic? Thanks.

These problems are normally framed from a standpoint of weak conjugate salts.

Here are the rules:
The conjugate of a strong acid (i.e. Cl-, NO3-, Br-), has NO basic properties. It didn't want an H+ when it was an acid, why would it want it back?
The conjugate of a strong base (Na+, K+, Ba+, etc) has NO acidic properties. same reasoning as above.
The conjugate base of a weak acid (like acetate, F-, HCO-), is slightly basic
The conjugate acid of a weak base (like NH4+) is slightly acidic


Now . . . you look at the salt. Some examples:
NaCH3COO -> Na+ + CH3COO- Na+: nothing. CH3COO-: slightly basic. overall, slightly basic.

NH4Cl --> NH4+ + Cl-. NH4+: slightly acidid. Cl-: nothing. Overall, slightly acidic.

If you have a situation where BOTH of the ions are conjugates of weak acids/bases (like NH4HCO3) - you need to look at the respective K values (Ka vs Kb). The one with a higher K value 'wins'.

hope this helps.