What would be the $$pH$$  of a solution obtained by mixing $$5g$$  of acetic acid and $$7.5g$$  of sodium acetate and making the volume equal to $$500\,mL?$$  $$\left( {{K_a} = 1.75 \times {{10}^{ - 5}},p{K_a} = 4.76} \right)$$

Solution :
$$\eqalign{ & pH = p{K_a} + \log \frac{{\left[ {{\text{salt}}} \right]}}{{\left[ {{\text{acid}}} \right]}} \cr & = 4.76 + \log \frac{{\frac{{7.5}}{{500}}}}{{\frac{5}{{500}}}} \cr & = 4.7 + \log \,1.5 \cr & = 4.87 \cr & {\text{Hence correct answer is}}\,\,4.76 < pH < 5.0 \cr} $$