Question
In which of the following solutions willacetic acid have the greatest percentage ionization? a. 0.10M CH3COOH b. 0.10M CH3COOH dissolved in 1.0M HCl c. 0.10M CH3COOH plus 0.10M CH3COONa d. 0.10M CH3COOH plus 0.20M CH3COONa In which of the following solutions willacetic acid have the greatest percentage ionization? a. 0.10M CH3COOH b. 0.10M CH3COOH dissolved in 1.0M HCl c. 0.10M CH3COOH plus 0.10M CH3COONa d. 0.10M CH3COOH plus 0.20M CH3COONa
Explanation / Answer
Dissociation of acetic acid: CH3COOH CH3COO- + H+ Dissolution of sodium acetate: Na+CH3COO- -----------------> Na+ +CH3COO- Acetic acid only dissociates a little, since it's a weak acid. Whensodium acetate is added, it dissociates completely. This increasesthe concentration of acetate, pushing the equilibrium to the left,making more acetic acid. This is the case in answer choices C andD, and results in a decreased percentage dissociation. Addition of CH3COOH into CH3COOH pushes the equilibrium to theright, making more acetate and hydrogen ions, resulting in anincrease in percentage dissociation. This is the case in answerchoice A. Addition of HCl to a solution of acetic acid increases hydrogen ionconcentration, so it pushes the equilibrium to the left, makingmore acetic acid. This results in decrease percentage dissociation,and is the case in answer choice B. *** The correct answer is A ***