Weak Acid Investigation

Section A. Introduction

After studying the differences between weak and strong electrolytes and completing a laboratory exercise regarding determining the pKa of a weak acid, I became intrigued by the factors that affected the partial ionization of a weak acid. After learning about Le Chatelier's ionization of a weak acid with the addition of a common ion. This investigation will observe the percent ionization of a weak acid when its ionic strength, a quantitative measure of the concentration of ions in a solution, is varied with the addition of salts. This investigation is done in hopes of finding an effective way to further ionize a weak acid, beyond the conditions of the surrounding environment, for application in the real world.

Section

The expression represents the acid dissociation constant Ka:

HA (aq) + H2O (l) ⇌ A-(aq) + H3O+(aq)

K_c=([A^- ][H_3 O^+])/([HA][H_2 O])íK_a=([A^- ][H_3 O^+])/[HA]

The degree of dissociation of a weak acid is a measurement of the strength of the acid. It is defined as the ratio of the number of ionized molecules and the number of molecules dissolved in water. The degree of dissociation, α, can be calculated using the following formula, assuming that α≪1: α=([H^+])/C_a =〖10〗^(-pH)/C_a where [H+] is hydrogen-ion concentration and Ca is concentration of acid (Lower, 2016). Percent ionization is simply the degree of dissociation multiplied by 100% to elicit a percentage of ions dissociated. The degree of dissociation for an acid will increase as the pH decreases and [H+] concentration increases because the original molecule is dissociating into H+ ions and acid anions.

Ostwald's dilution law is a relationship between the dissociation constant and the degree of dissociation of a weak electrolyte (Stock, 1997). Ostwald suggested that the law of mass action could be applied to systems of dynamic equilibrium between ions and unionized molecules of the electrolyte in solution. For very weak electrolytes like acetic acid, the law suggests that percent ionization increases upon

Solvation is an interaction of a solute with the solvent, which leads to stabilization of the solute species in solution. In the solvated state, an ion in a solution is surrounded by solvent molecules, forming a shell of ions which help prevent the solvent from reversing towards its original molecule. A higher concentration of inert ions in the solution shields the ions in the equilibrium with counter-cations and counter-anions in their ionic atmohsphere and decreases the tendency for ions to favor the reverse reaction and form the original molecule (Meyerhoff,