Titration, how does it work?

[destroythemcat]

I'm a bit confused about titrations.

When an acid is being titrated by a strong base.

Acid before titration: HA-->H+ + A-

When the strong base is added, lets say NaOH:

1. Do the hydroxide ions reacts with H+ --> h2O and shift the equation to the right

2. Or do the hydroxide ions react with HA causing the reaction to shift?

hope someone can help me out

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[kraskadva]

the OH- reacts with the H+ to form water.
A- & B+ can either hang out in solution as spectator ions or come together to form a salt and precipitate out of solution.

If you're starting with a strong acid, all the HA has dissociated to H+ & A- before the base is added and the equation doesn't shift back.
If you're starting with a weak acid, as the OH- removes H+ from solution, the initial HA --> H+ & A- can shift further to the right (Le Chatlier's Principle) but will still eventually reach equilibrium and then be overwhelmed by the OH- as you continue to add base.

 

[destroythemcat]

thank you!