Textbook clarification: weak acids and bases

[DHavo_1E]

Hello,

Could someone explain what the textbook means when it says that a solution of a weak acid in water would have a very, very low concentration of OH- ions to maintain autoprotolysis equilibrium? Thank you!

[AArmellini_1I]

So because it is a very weak acid/base it only dissociates by a small concentration. Therefore, since your KA or B is [products] / [reactants] and only a small concentration will dissociate into the product, Ka or B is a very small number divided by a much bigger number which = a very small number :) So to add on, you only need a small concentration of OH- ions to maintain equilibrium.

[DHavo_1E]

So because it is a very weak acid/base it only dissociates by a small concentration. Therefore, since your KA or B is [products] / [reactants] and only a small concentration will dissociate into the product, Ka or B is a very small number divided by a much bigger number which = a very small number :) So to add on, you only need a small concentration of OH- ions to maintain equilibrium.

Hi,
This helped me understand a lot more thank you! Also, are the OH- ions the conjugate bases of water? Thank you!!

[Rafsan Rana 1A]

OH- are the conjugate base of water. However, if water reacts with an acid, wouldn't it act as a base thus it would have a conjugate acid of hydronium ions?