Determine if the following salt is neutral, acidic or basic. If acidic or basic, write the appropriate equilibrium equation for the acid or base that exists whe (CH₃)₂NH₂ClO₄

Question

Determine if the following salt is neutral, acidic or basic. If acidic or basic, write the appropriate equilibrium equation for the acid or base that exists when the salt is dissolved in aqueous solution. If neutral, simply write only NR. Be sure to include the proper phases for all species within the reaction. Remove all spectator ions. (CH₃)₂NH₂ClO₄

Answer 1

In order to determine if a salt is acidic or basic, you must be familiar with the lists of strong acids as well as the concept of conjugate acid/base pairs. Remember, if an acid is strong, it’s conjugate is a super weak base, and if a base is strong, it’s conjugate is a super weak acid.

Steps:

Write the salt in ion components

Write the reaction of each component with water (optional if you know how to make conj acid base pairs)

Determine the strength of the “parent” acid or base

Determine if the conjugate will affect the pH based on the strength of the parent acid or base

First break the salt into its ion components. Then, this is what you are looking for:

If one of the components is the conjugate of a strong acid or base, that component does NOT contribute to the pH (it is neutral).

If one of the components is the conjugate base of a weak acid, the solution will be slightly basic.

If one of the components is the conjugate acid of a weak base, the solution will be slightly acidic.

The salt is (CH3)2NH2ClO4. Break it apart:

(CH3)2NH2ClO4 —> (CH3)2NH2+ + ClO4-

Next, to determine if these act as conjugate acids or bases, we are looking for how these ions interact with water. If you know how to make conjugate pairs, just write the corresponding parent acid/base that matches with each ion.

(CH3)2NH2+ + H2O —> (CH3)2NH + H3O+

Being positively charged, CH3)2NH2+ will act as a proton donor to make H3O+. This means it is a conjugate acid of the parent base (CH3)2NH created on the other side.

ClO4- + H2O —> HClO4 + OH-

Being negatively charged, ClO4- will act as a proton acceptor to make OH-. This means it is the conjugate base of the parent acid HClO4 created on the other side.

Lastly, we determine the strength of the “parent” acid and base to determine if the conjugate will affect the pH. You can use a list of strong acids and bases to help.

(CH3)2NH is a weak base. This means (CH3)2NH2+ is a weak conjugate acid and will cause the solution to be slightly acidic.

HClO4 is a strong acid. This means ClO4- will have no effect on the pH (neutral).

Overall, when the salt CH3)2NH2ClO4 breaks apart, the solution will be acidic