What is a Buffer?

Personally, I think buffers are one of the most difficult chemistry concepts ever. So what even is a buffer?

• Resists change in pH when acid (H3O+) or base (OH-) is added
• Must be at equilibrium
• It should put you in the 1/2 equivalence point

(I got the graph from: http://chemistry.about.com/od/acidsbase1/ss/titrationcurves_2.htm)

But how can you form one? Well, that is where it gets a bit tricky...

• Weak acid + its conjugate base (1:1 ratio for moles/L)
• Weak base + its conjugate acid (1:1 ratio for moles/L)
• Weak acid + salt (1:1 ratio for moles/L)
• Weak base + salt (1:1 ratio for moles/L)
• Weak acid + strong base (1:1/2 ratio for moles/L)
• Weak base + strong acid (1:1/2 ratio for moles/L)
• Strong acid + strong base (1:1/2 ratio for moles/L)
• Strong base + strong acid (1:1/2 ratio for moles/L)

So basically, if there is any strong acid/base, it must only be half the molarity of what else is being added to be a buffer so that only half of the other reactant is being neutralized. Just about everything else can be in a 1:1 ratio.

What about a salt and a strong acid?
NO!!
Example: HCl
If you do that, the H+ will be given to the H2O, so the products will be Cl- and H3O+. If you try to get the equilibrium to go backwards, the H+ will not stick with the Cl- because strong acids and strong bases always dissociate.

Are you still confused? Well, maybe this video can help you out. It definitely helped me!
https://www.youtube.com/watch?v=by312TXbKfI

Best of luck!

Kaylee