<u>Answer:</u> The mass of sodium acetate that must be added is 30.23 grams
<u>Explanation:</u>
To calculate the number of moles for given molarity, we use the equation:

Molarity of acetic acid solution = 0.200 M
Volume of solution = 1 L
Putting values in above equation, we get:

To calculate the pH of acidic buffer, we use the equation given by Henderson Hasselbalch:
![pH=pK_a+\log(\frac{[CH_3COONa]}{[CH_3COOH]})](https://tex.z-dn.net/?f=pH%3DpK_a%2B%5Clog%28%5Cfrac%7B%5BCH_3COONa%5D%7D%7B%5BCH_3COOH%5D%7D%29)
We are given:
= negative logarithm of acid dissociation constant of acetic acid = 4.74
![[CH_3COOH]=0.200mol](https://tex.z-dn.net/?f=%5BCH_3COOH%5D%3D0.200mol)
pH = 5.00
Putting values in above equation, we get:
![5=4.74+\log(\frac{[CH_3COONa]}{0.200})](https://tex.z-dn.net/?f=5%3D4.74%2B%5Clog%28%5Cfrac%7B%5BCH_3COONa%5D%7D%7B0.200%7D%29)
![[CH_3COONa]=0.364mol](https://tex.z-dn.net/?f=%5BCH_3COONa%5D%3D0.364mol)
To calculate the mass of sodium acetate for given number of moles, we use the equation:

Molar mass of sodium acetate = 83.06 g/mol
Moles of sodium acetate = 0.364 moles
Putting values in above equation, we get:

Hence, the mass of sodium acetate that must be added is 30.23 grams