Answer : The mass of sodium acetate is, 1.097 grams.
Explanation : Given,
The dissociation constant for acetic acid = 
Concentration of acetic acid (weak acid)= 0.20 M
volume of solution = 125. mL
pH = 4.47
First we have to calculate the value of
.
The expression used for the calculation of
is,

Now put the value of
in this expression, we get:



Now we have to calculate the concentration of sodium acetate (conjugate base or salt).
Using Henderson Hesselbach equation :
![pH=pK_a+\log \frac{[Salt]}{[Acid]}](https://tex.z-dn.net/?f=pH%3DpK_a%2B%5Clog%20%5Cfrac%7B%5BSalt%5D%7D%7B%5BAcid%5D%7D)
Now put all the given values in this expression, we get:
![4.47=4.74+\log (\frac{[Salt]}{0.20})](https://tex.z-dn.net/?f=4.47%3D4.74%2B%5Clog%20%28%5Cfrac%7B%5BSalt%5D%7D%7B0.20%7D%29)
![[Salt]=0.107M](https://tex.z-dn.net/?f=%5BSalt%5D%3D0.107M)
Now we have to calculate the mass of sodium acetate.



Therefore, the mass of sodium acetate is, 1.097 grams.