Weak acid/base and Conjugate acid/base help.

[pharmvsu]

---

Members do not see this ad.

So I understand that the conjugate base of an acid has 1 less H+ and all that. But i'm working with buffer equations and when you are given an acid and a base how do you know which one is the weak one and which one is the conjugate?

 

[keefis]

Without using a chart you can guess by applying some rules you learn in ochem. The more stable the conjugate is without the H+, will translate into a stronger acid. Not sure what you mean about the buffer.

 

[UofAHogs]

So I understand that the conjugate base of an acid has 1 less H+ and all that. But i'm working with buffer equations and when you are given an acid and a base how do you know which one is the weak one and which one is the conjugate?

The strength of the conjugate base will be inverse in strength to that of the acid. As the acids increase in strength, the strength of the conjugate bases will decrease.

If you take the time to familarize yourself with the strengths of acids, you should be able to reason the strength of the conjugate bases.

 

[Busta919]

A strong acid = weak conjugate base
Weak acid = Strong conjugate base

 

[liebht90]

They are conjugates to each other. So for example HCl -----> H+ + Cl-
HCL is a strong acid and dissociates into the acidic H+ proton and the conjugate weak base of Cl-. The conjugate of the Cl- would be the protonated form as HCl. As far as knowing if something is weak, its pretty simple to memorize all the strong acids and bases, most chem textbooks have them. I believe another rule of thumb used is if the Ka or Kb is less than 1 it is considered weak, whereas if it is over 1 it wants to go to completion more. I'm pretty sure this is right... anyone able to back me up? Haha