How many grams of should be added in 500 ml of acetic acid solution to get a buffer solution of maxi — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

Maximum buffer capacity occurs when the pH is exactly equal to the $pK_a$ of the weak acid, which happens when the concentration of the salt equals the concentration of the acid ($[\text{Salt}] = [\text{Acid}]$). To achieve this, exactly half of the weak acid must be neutralized by the strong base. Initial moles of acetic acid = $500 \text{ ml} \times 2 \text{ M} = 1.0 \text{ mole}$. We must neutralize $0.5 \text{ moles}$, requiring $0.5 \text{ moles}$ of NaOH. The mass of NaOH = $0.5 \text{ moles} \times 40 \text{ g/mol} = 20.0 \text{ g}$. Therefore, correct answer is A.