To not suppress the degree of dissociation of acetic acid, we need to avoid adding substances that can react with or form complexes with the acetic acid molecules. Acetic acid is a weak acid, meaning it partially dissociates in water to form acetate ions and hydronium ions (H3O+). The degree of dissociation of acetic acid refers to the extent to which it dissociates into ions in a solution.
The following substances, when added to a solution of acetic acid, will not suppress its degree of dissociation:
Inert gases (e.g., nitrogen, argon, helium): These gases do not react with acetic acid and do not have any influence on its degree of dissociation.
Non-reactive salts (e.g., sodium chloride, potassium sulfate): These salts dissociate into ions in the solution, but they do not participate in any significant chemical reaction with acetic acid.
Solvents that do not interact with acetic acid: If you add a solvent that does not affect the interactions between acetic acid molecules, it will not suppress the degree of dissociation. Examples include many nonpolar solvents that do not form hydrogen bonds with acetic acid.
Weak acids (e.g., formic acid): Adding a weak acid to a solution of acetic acid will not significantly affect its degree of dissociation, as both acids will undergo similar levels of dissociation.
Remember that adding a strong acid or a strong base to the solution of acetic acid would indeed suppress its degree of dissociation. Additionally, certain metal ions or strong reducing agents might also interact with acetic acid and reduce its dissociation to some extent.