Question

Acetic acid has a Ka of 1.8×10−5. Three acetic acid/acetate buffer solutions, A, B, and C, were made using varying concentrations:______[acetic acid] ten times greater than [acetate],[acetate] ten times greater than [acetic acid], and[acetate]=[acetic acid].Match each buffer to the expected pH.pH = 3.74 ; pH = 4.74 ; pH = 5.74

Answer 1

A: pH = 3.74

B: pH = 5.74

C: pH = 4.74

Step-by-step explanation:

According to the Henderson-Hasselbach equation for buffers, we know that
`pH = pK_a + log(([A^-])/([HA]))`. Firstly, let's find the
`pK_a` value:

`pK_a = -log(K_a) = -log(1.8\cdot 10^-5) = 4.74`

Now, for buffer A:

`([A^-])/([HA])=([CH_3COO^-])/([CH_3COOH])=(1)/(10)`

This means:

`pH = 4.74 + log((1)/(10)) = 3.74`

Similarly, for buffer B:

`([A^-])/([HA])=([CH_3COO^-])/([CH_3COOH])=(10)/(1)`

This means:

`pH = 4.74 + log((10)/(1)) = 5.74`

Similarly, for buffer C:

`([A^-])/([HA])=([CH_3COO^-])/([CH_3COOH])=(1)/(1)`

This means:

`pH = 4.74 + log((1)/(1)) = 4.74`