Question

Explain why a buffer always consists of a weak acid and its conjugate base, rather than a strong acid and base?

Answer 1

Beacause strong acid and strong base will react and form salt and water. It will notb act as buffer

Answer 2

Acetic acid is a monoprotic acid, with one acidic hydrogen atom. It contains the acid group of carbon-containing molecules, -COOH and is called a carboxylic acid. The Lewis structure of acetic acid and its conjugate base acetate ion are shown below



For convenience, we will write CH₃COOH to denote the acid formula. In water, acetic acid establishes an equilibrium between the weak acid, acetic acid, and the conjugate base, acetate ion.

CH₃COOH + H₂O H₃O⁺ + CH₃COO^- (1)

The equilibrium constant, K_a, for this reaction is written

(2)

For acetic acid, the value of K_a equals 1.76 x 10

Answer 3

It is because strong acid and strong base will react completely to form salt and water.

Answer 4

pH buffers usually consist of a weak acid and its salt because:

1. a weak acid does not completly dissociate into its component parts: H+ and its conjugate base
-for example: HC2H3O2 does not completely dissociate to H+ and C2H3O2-

2. when a salt containing its conjugate base is added, it will complietly dissociate:
-for example: NaC2H3O2 will completely dissociate to Na+ and C2H3O2-

3.So when a strong acid is added to the buffer solution, then the H+ from the strong acid will react with the conjugate base to from the weak acid thus the pH will not change
-for example: HCl is added. then the H+ from HCl will react with the C2H3O2- to form HC2H3O2, the weak acid which will not dissociate completely thus the pH will not change

Answer 5

The significance of the pairing is that the solution is in equilibrium of H+ and OH- ions, if you increase pH (by addin OH-) then the equilibrium is disturbed and the system opposes this (Le Chatillier's principle) by having an amount of acid and base molecules in your solution, the solution has the ability to "mop up" extra H+ and OH- ions introduced to the solution.
If you change the weak acid/base then you will change the equilibrium pH of your buffer. Without looking it up I cannot be certain, but I believe increasing the alkylic chain (eth-->prop) you make the anion more stable due to electron induction, thus increase the proton concentration in your solution and reduce the pH.

Answer 6

The significance of the pairing is that the solution is in equilibrium of H+ and OH- ions, if you increase pH (by addin OH-) then the equilibrium is disturbed and the system opposes this (Le Chatillier's principle) by having an amount of acid and base molecules in your solution, the solution has the ability to "mop up" extra H+ and OH- ions introduced to the solution.

If you change the weak acid/base then you will change the equilibrium pH of your buffer. Without looking it up I cannot be certain, but I believe increasing the alkylic chain (eth-->prop) you make the anion more stable due to electron induction, thus increase the proton concentration in your solution and reduce the pH.

pH buffers usually consist of a weak acid and its salt because:

1. a weak acid does not completly dissociate into its component parts: H+ and its conjugate base
-for example: HC2H3O2 does not completely dissociate to H+ and C2H3O2-

2. when a salt containing its conjugate base is added, it will complietly dissociate:
-for example: NaC2H3O2 will completely dissociate to Na+ and C2H3O2-

3.So when a strong acid is added to the buffer solution, then the H+ from the strong acid will react with the conjugate base to from the weak acid thus the pH will not change
-for example: HCl is added. then the H+ from HCl will react with the C2H3O2- to form HC2H3O2, the weak acid which will not dissociate completely thus the pH will not change