Is Perchloric (HClO4) an acid or base? Strong or Weak - Conjugate base

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is hclo4 an acid or base?

Perchloric acid is a mineral acid that appears as a colorless liquid having the chemical formula HClO4. It is odorless and miscible in water. It is corrosive to tissue and metals.

In this article, we will discuss Is HClO4 an acid or base? Its nature(Strong or weak, Conjugates acid-base pairs, etc.

So, Is HClO4 an acid or base? HClO4 is considered an acid because on dissolving in an aqueous solution it dissociates into two ions (H+ and ClO4) and anything that release proton ion in solution considered as the acid in nature. 

Name of MoleculePerchloric acid
Chemical formulaHClO4
Molar mass100.46 g·mol−1
NatureStrong acid
Conjugate baseClO4

Why HClO4 is an acid?

To Know Why HClO4 is acting as an acid? We have to look into the famous theory given by Arrhenius for the acid compounds.

This theory state that a compound is said to be acid when it produces H+ ions on dissolving in an aqueous solution and forms H3O+ ions when combining with the water molecule.

Now have a look at HClO4 dissociation in an aqueous solution.

HClO4 → H+ + ClO4

As on dissolving HClO4 in an aqueous solution, it dissociates in two ions H+ and ClO4. Then, a proton ion(H+) combines with a water molecule and forms H3O+.

⇒ HClO4(g) + H2O(l) H3O+(aq) + ClO4(aq)

why HClO4 is an acid?

Also, Arrhenius sate that an acid is a compound that increases the concentration of hydrogen ion(H+) in solution.

In the case of the HClO4 compound, when dissolved in an aqueous solution it liberates H+ ions, hence increases the concentration of hydrogen ion in the final solution.

So, the HClO4 compound definitely following all conditions needs to meet for the Arrhenius acid compound. Hence, we can say the HClO4 compound is an Arrhenius acid compound.

Now we look for another most important acid-base theory that is the Bronsted-Lowry theory.

This theory states a compound is classified as an acid when it donates the proton to other species and itself forms a conjugate base. And a compound is classified as a base when it accepts the proton from other species and itself forms a conjugate acid.

In short as per Bronsted-Lowry theory

  • A Bronsted-Lowry acid is a proton (hydrogen ion) donor.
  • A Bronsted-Lowry base is a proton (hydrogen ion) acceptor.

Let’s check whether HClO4 fulfills the requirement for classifying as Bronsted-Lowry acid or not.

Consider the reaction of HClO4 reacting with NH3.

Is HClO4 Bronsted-Lowry acid?

Here, HClO4 reacts with ammonia and donates the proton which is accepted by NH3 and itself forms ClO4 conjugate base.

Illustration of above reaction (HClO4 with NH3):-

  • HClO4 act as Bronsted-Lowry acid as it donates the proton and forms a conjugate base.
  • NH3 acts as a Bronsted-Lowry base as it accepts the proton from HClO4 and forms a Conjugate acid.
  • Ammonium ion (NH4+) is the conjugate acid of the base NH3.
  • Perchlorate ion(ClO4) is the conjugate base of the acid HClO4.

Is HClO4 strong acid or weak acid?

A strong acid is something that completely dissociates or is 100% ionized in a solution. Some examples of strong acid – HCl, HBr, HNO3, H2SO4, etc.

Also, Read:-

Characteristics of strong acid:-

  • They are strong electrolytes and have high conductivity.
  • Their pH value lies between 1 to 3.
  • They dissociate completely and release a large number of  H+ ions in a solution.

A weak acid is something that is not able to dissociate completely or partially dissociate in a solution. Some examples of a weak acid – CH3COOH, H3PO4, HCN, NH4+, etc.

Also, Read:-

Characteristics of Weak acids:-

  • They are weak electrolytes and have less conductivity as compare to strong acids.
  • Their pH value lies between 3 to 7.
  • They ionized partially to produce H+ in a solution.

Now, Is HClO4 a strong or weak acid? HClO4 is a strong acid because it readily dissociates in an aqueous solution, which means no dissociated parts of it remain in the solution, all parts completely break off and are ionized in an aqueous solution.

As on dissolving HClO4 in an aqueous solution, no parts of H+ remain bound to it, which means the concentration of hydrogen ion increased in the solution. Hence, we can say, HClO4 is a strong acid or act as a strong acid.

is hclo4 strong acid or weak acid

Here as shown in the figure, HClO4 acid dissociates completely in H+ and ClO4 with no undissociated acid present in solution. Hence, Perchloric acid is a strong acid.

Also, the acid dissociation constant value(Ka) for HClO4 is ca. 1010. [check here]

The acid dissociation constant (Ka) is a quantitative measure of the strength of an acid in solution

⇒ If the value of the dissociation constant of acid is greater than 1 (Ka >> 1), then the nature of the compound is a strong acid.

⇒ If Ka << 1, then the nature of the compound is a weak acid.

Here’s the list of some common acids and bases with their strength.

why hclo4 is strong acid

What is the conjugate base of HClO4?

Whenever the acid donates the proton, it converts into the conjugate base and whenever the base accepts the proton, it converts into the conjugate acid.

Conjugate acid is an acid that formed when the base compound gains one proton and the conjugate base is a base that formed when the acid compound loses one proton.

The concept of conjugate acid-base pair.

  • A very strong acid always forms a weak conjugate base.
  • A very strong base always forms a weak conjugate acid.
  • A very weak acid always forms a strong conjugate base.
  • A very weak base always forms a strong conjugate acid.

As per Bronsted-Lowry or Arrhenius theory, HClO4 is acid and loses one proton when combines with the water molecule and forms a base known as the conjugate base of an HClO4 acid.

The conjugate base of HClO4 is ClO4.

what is the conjugate base of hclo4

Uses of Perchloric acid

  1. It is used to separate potassium from sodium.
  2. It is used as a catalyst and as a reagent.
  3. It is used to make explosive materials.
  4. It is used as a precursor to perchlorate salts which is used in rocket fuels.
  5. It is also used for electropolishing or etching of molybdenum, aluminum, and other metals.

Properties of Perchloric acid

  1. It is corrosive to metal and tissue.
  2. It has a pKa lower than -9.
  3. It is one of the strongest mineral acids and stronger acids than H2SO4 and HNO3.
  4. It has a boiling point of 203 °C and a melting point of −17 °C.
  5. It is a non-flammable and powerful oxidizer.

Summary

Perchloric acid is an inorganic or mineral acid that appears as a colorless liquid and is generally odorless in nature. It is one of the stronger acids and its aqueous solution is stronger than sulfuric acid and nitric acid. At last, with some important points of this article on Is HClO4 an acid or base? we will finish it.

  • HClO4 is acid as it liberates the H+ ions when dissolved in solution and increases the concentration of hydrogen ions in the final solution.
  • The conjugate base of HClO4 is ClO4, as it formed after the removal of one proton from HClO4.
  • Is Perchloric (HClO4) is a strong or weak acid? HClO4 is not only strong acid but it is one of the strongest minerals acids as it completely breaks off when dissolved in an aqueous solution, which means it doesn’t leave any traces of undissociated parts in a solution, all parts of it completely ionized in solution and increases the concentration of hydrogen ions.
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