Question

What will be the pH value of a solution of $500mL$ containing $5g$ acetic acid and $7.2g$ of sodium acetate? $K_a=1.8\times {10}^{-5}$ at ${25}^{o}C$.

Answer 1

Number of moles of sodium acetate=$\frac{7.2}{80}=0.09moles$

Number of moles of acetic acid=$\frac{5}{50}=0.01moles$

$pH=log\frac{\left[Salt\right]}{\left[Acid\right]}-\log K_a=-log(1.8\times {10}^{-5})+log\left(9\right)=4.82$