Salts that Produce Basic Solutions

A basic salt dissolves in water to form a solution with pH greater than 7.0.


Key Takeaways

Salt, the basic type

In acid-base chemistry, a salt is an ionic compound formed when an acid reacts with a base.As such, salts contain cations (positively charged ions) and anions (negatively charged ions) and are electrically neutral (without a net charge).Salt ions can consist of inorganic ions, such as chloride (Cl*), organic acetate (CH3CO*), monatomic fluoride (F*), and polyatomic ions, such as sulfate (SO42−).

The Reaction of a Basic Salt in Water

In this section, we will cover basic salts.Why would a basic salt be basic?.As a result, the anion in the salt is the conjugate base of a weak acid.

(ext[B])*+(ext[aq])+(ext[H]+(ext[l])

For example, sodium bicarbonate is a basic salt, NaHCO3.It's a conjugate base of carbonic acid, a weak acid.In this regard, it reacts with water as follows:

HCO_3*-(ext[aq]) + H2O (ext[l])

As it has the ability to deprotonate water and provide a basic solution, sodium bicarbonate is a basic salt.

Basic salts include:

As you can see, the anion is the conjugate base of all of these weak acids (carbonic acid, bisulfate (second dissociation step of sulfuric acid), acetic acid, hydrocyanic acid, hydrogen sulfide).

Conjugate Bases of Weak vs. Strong Acids

It is important to remember that a salt can only be basic if it contains the conjugate base of a weak acid.Chloride (Cl–), for example, is the conjugate base of HCl.Although HCl is a strong acid, the Cl– ion cannot deprotonate water because it is not basic.


*

Salts With a Hydrolyzable Cation

When dissolved in water, acidic salts yield solutions with a pH less than 7.0. .Ammonium salts or organic compounds with protonated amine groups contain acidsic protons in the cation.Some examples are:

A salt containing these cations with a neutral base, such as ammonium chloride (NH4Cl), is called an acid salt.

Salts With Hydrolyzable Protons in the Anion

An anion in an acid salt can also contain an acidic proton.Examples of anions that are acidic include:

Protons in these anions will weakly dissociate in water.So they will produce weakly acidic solutions in water when salts containing them are present, such as potassium bisulfate.

Determining Acidity or Alkalinity of a Hydrolyzable Ion

As we learned in the previous concept, salts containing the bicarbonate ion (HCO3–) are basic, whereas salts containing the bisulfate ion (HSO4–) are acidic.Compared with its Ka and Kb values, the hydrolyzable ion will be acidic if Ka > Kb, and basic if Kb > Ka.



Key Takeaways

It neutralizes In anhydrolysis You are salty

Summary of Acidic and Basic Salts

Depending on their cations and anions, salts can form acidic or basic solutions if they are hydrolyzable (react in water).Strong bases and weak acids react to form basic salts; for instance, sodium hydroxide reacts with acetic acid to form water and sodium acetate.As a basic salt, sodium acetate can deprotonate water, thus raising the pH of a solution.

Acid salts are formed by neutralizing strong acids with weak bases.Acid is formed by the conjugate acid of the weak base.In the reaction between hydrochloric acid (a strong acid) and ammonia (a weak base), water is produced as well as ammonium chloride.Since ammonium ion contains a proton, it's an acid salt.

Salts in Which Both Ions Hydrolyze

Here is a more complex scenario, in which a salt contains both cations and anions that can participate in hydrolysis.A good example of such a salt is ammonium bicarbonate, NH4HCO3. As with all ammonium salts, it is highly soluble, and demonstrates the following dissociation in water:

Int[NH]_4 Int[CO]_3 ( Int[s])

Although we have discussed this already, the ammonium ion acts as a weak acid in solution, while the bicarbonate ion acts as a weak base.Reactions:

Isolate [NH]_4*+ ( ext{aq})+ ext{H}_2 ext{O}( ext{l})

HCO_3*-( ext[aq])+ H_2 ext{O}( ext{l})

.Compare the Ka and Kb values for each ion to determine the answer.As seen in the graph, the value of Kb for bicarbonate is greater than the value of Ka for ammonium.Bicarbonate is slightly alkaline, while ammonium is acidic, and a solution of ammonium bicarbonate in pure water will have a pH > 7.0.