Question

Calculate the

pH of the acetate buffer CH3COOH + CH3COONa, containing 0.01 of each of the compound. Ka= 1.8×10^-5​

Answer 1

`\large \boxed{4.7}`

Step-by-step explanation:

HA + H₂O ⇌ H₃O⁺ + A⁻

(a) Calculate pKₐ

`\text{p}K_{\text{a}} = -\log \left (K_{\text{a}} \right ) =-\log(1.8 * 10^(-5)) = 4.74`

(b) Calculate the pH

We can use the Henderson-Hasselbalch equation to get the pH.

`\begin{array}{rcl}\text{pH} & = & \text{pK}_{\text{a}} + \log \left(\frac{[\text{A}^(-)]}{\text{[HA]}}\right )\\\\& = &4.74 +\log \left((0.01)/(0.01)\right )\\\\& = & 4.74 + \log1.0 \\& = & 4.74 +0.0\\& = &4.7 \\\end{array}\\\text{The pH is $\large \boxed{\textbf{4.7}}$}`