EK - acid-base titration

[Monkeymaniac]

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Let's say we titrate weak monoprotic acid HA with strong base. At half-eq. point, There are equal concentration of A- and HA.

The dissociation reaction for HA is HA + H20 -> H3O+ + A-.
Since HA is weak acid, Ka is small, say 10^-10.

Then isn't the Keq for reverse reaction huge? which is 1/10^-10 = 10^10?
Then why isn't good amount of A- converted back to HA? I'm really confused. Would anyone please clarify? Thanks in advance.

 

[G1SG2]

Let's say we titrate weak monoprotic acid HA with strong base. At half-eq. point, There are equal concentration of A- and HA.

The dissociation reaction for HA is HA + H20 -> H3O+ + A-.
Since HA is weak acid, Ka is small, say 10^-10.

Then isn't the Keq for reverse reaction huge? which is 1/10^-10 = 10^10?
Then why isn't good amount of A- converted back to HA? I'm really confused. Would anyone please clarify? Thanks in advance.

I would say that since it's a pretty week acid with a small Ka, the conjugate base won't be that strong, and wouldn't have a large Keq either. Someone can correct me if I'm wrong.