March 28, 2024, 10:22:17 AM
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Topic: Am I understanding the concept of Ka, Pka, conjugate acid and base correctly?  (Read 2666 times)

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Offline parad0x

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Here's my understanding:

1) Pka and Ka are inversely related, so a higher Pka means a smaller Ka, and vice versa
2) Since Ka is a product to reactant ratio, a higher Ka means more product formed, which means a stronger acid
3) Once and acid-base reaction has finished proceeding either forward or backwards, it has reached equilibrium
4) An acid will form a conjugate base, and a base will form a conjugate acid
5) The stronger an acid, the weaker a conjugate base. Why?

Simply because a stronger acid will dissolve to almost 100% (let's say for the sake of the explanation, to 99.999%). That means that we now have 0.001% acid left for 99.999% base in the reaction, at equilibrium. Therefore, the 0.001% strong acid is counter-balanced by 99.999% weak base,k so the base has to be very weak, otherwise due to the much larger quantity, we wouldn't have an equilibrium

Offline Rutherford

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1), 2), 4) and 5) are good.
3) Dynamic equilibrium isn't reached when the forward and the backward reactions stop. Do you know when it is reached?

For 5), read this http://www.chembuddy.com/?left=pH-calculation&right=bronsted-lowry-theory.

Offline parad0x

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1), 2), 4) and 5) are good.
3) Dynamic equilibrium isn't reached when the forward and the backward reactions stop. Do you know when it is reached?

For 5), read this http://www.chembuddy.com/?left=pH-calculation&right=bronsted-lowry-theory.

Thanks! Although I didn't express myself correctly for #3

I believe equilibrium reaches when the forward and backward reactions undergo equal rate, thus giving no more visible changes, but the forward/backward reactions never truly stop

Offline Rutherford

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That's correct.

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