Is NH4Br a Base or an Acid?

The ionic salt of Hydrogen Bromide and Ammonia is ammonium bromide (NH4Br). Bromide (Br-) ions oxidise to Bromine when exposed to air, resulting in white, odourless granules that turn yellow when exposed to air (Br2).

It’s the ammonium salt of hydrobromic acid, with a 1:1 ratio of ammonium and bromide ions. In an aqueous solution, it is a powerful electrolyte that conducts electricity.

It is made by combining Hydrogen Bromide (HBr) and Ammonia in a direct reaction (NH3). The response is written as follows:

NH4Br from HBr + NH3.

So, is NH4Br a basic or an acid? An acid is NH4Br. It’s an ammonia and hydrogen bromide (HBr) salt (NH3). It’s worth noting that HBr is a strong acid, whereas NH3 is a weak base. Strong acid and weak base salts are acidic in nature, thus NH4Br is acidic as well. In water, it has a pKa value of 5 and a pH of less than 7.

In nature, why is NH4Br acidic?

The neutralisation reaction is characterised as a reaction between an acid and a base, and the end-product created in such reactions is known as the salt.

Because the strength of the fundamental molecules determines the qualities of the salt, its acidity or basicity is obtained from the constituent acid or base.

The simplest way to evaluate whether salt is acidic or basic is to look at its main parts, namely sodium chloride and potassium chloride.

Strong acid and strong base salts have a pH of 7 and are therefore neutral.

The salts of a weak acid and a strong base are basic if their pH is greater than 7.

Strong acid and weak base salts have a pH of less than 7.

Hydrogen Bromide is a strong acid, whereas Ammonia is a weak base in the case of NH4Br. As previously stated, the salt takes on the properties of the stronger molecule, making NH4Br acidic.

We can also learn about a substance’s nature by looking at its dissociation equation or the ions it produces in an aqueous solution.

In an aqueous solution, the dissociation equation for NH4Br is as follows:

NH4Br ——> NH4+ + Br – NH4+ + Br – NH4+ + Br – NH4+ + Br –

Br- is the conjugate base of HBr in this case. We know that HBr is a strong acid, and that strong acids’ conjugate bases are weak bases.

Because the Br- ion is such a weak base, it cannot hydrolyze any more.

NH3 is also a weak base, because weak bases produce powerful conjugate acids.

As a result, the NH4+ ion generated is extremely powerful in nature.

As a result, it may be argued that Br- ions (due to their inability to hydrolyze further) have no bearing on the acidity or basicity of this solution.

However, in the aqueous solution, ammonium ions (NH4+) lose protons and create ammonia (NH3) and hydronium ions (H3O+).

The acidity of the aqueous solution of NH4Br is caused by the hydronium ions generated by the dissociation of ammonium ions.

I also wrote an article about KNO3 a few days ago, which you can read here: Is KNO3 an Acid or a Base.

What exactly is an acid?

Acids are compounds that release their proton when dissolved in an aqueous solution. Acids have a sour flavour and are caustic by nature.

HBr, H2SO4, CH3COOH, and other acids are examples.

The ease with which acids lose their proton affects their strength, and the acids are classified as strong acids or weak acids depending on this.

Strong acids are those that have an easy time giving up their protons. For instance, HBr, H2SO4, and so on.

Weak acids, on the other hand, are those in which the protons are firmly attached and do not easily detach. Weak acids include CH3COOH, HCN, and others. The full dissociation of weak acids necessitates a significant amount of energy.

In an aqueous solution, however, powerful acids rapidly dissociate or ionise.

The acids have the following qualities in addition to being proton donors:

A pH of less than 7 is required.

The blue litmus will turn red.

To produce the salt, it must react with a complimentary base.

NH4Br’s pH

The acidity or basicity of a solution is determined by its pH. Any substance’s pH value spans from 1 to 14 on the pH scale, with pH 7 being neutral (it is the pH of water).

A substance is termed acidic if its pH value is less than 7, and it is considered alkaline if its pH value is greater than 7.

We already know that NH4Br is an ionic salt with a strong acid and a weak base. As a result, NH4Br’s pH should be less than 7.

The pH of a 1 M NH4Br solution is calculated as follows:

The hydrogen ion concentration is computed as follows:

[Ka * M] = [H+]

Because Ka = NH4Br has a value of 5.6 * 10-10,

We’re also working out the hydrogen ion concentration in a 1 M NH4Br solution.

As a result, [H+] = 5.6 * 10-10 * 1.

= 2.3 * 10-5 = 2.3 * 10-5 = 2.3 * 10-5 =

The pH of a 1 M solution can now be determined using the following formula:

pH = – log [H+] pH = – log [H+] pH = – log [H

= – log [2.3 X 10-5] = – log [2.3 X 10-5] = – log [2.3

= [log 2.3 – 5 log 10] = – [log 2.3 – 5 log 10] = – [log 2.3 –

equals 4.63

Because the pH of NH4Br is less than 7, it is apparent that it is acidic in nature.

Why is NH4Br not considered a base or basic salt?

The definition of the base can be found in several theories. The following are three significant ones that determine base:

A molecule with an unshared pair of electrons that can be handed away to another molecule, according to Lewis theory.

The Bronsted-Lowry theory describes a molecule that can easily absorb a proton that has been given away by another molecule.

A molecule that creates the hydroxide ion (OH-) in a solution, according to the Arrhenius theory.

None of the above-mentioned definitions apply to NH4Br.

It lacks an accessible pair of electrons, does not absorb a proton from a solution, and creates hydronium ions (H3O+) in a solution instead of hydroxide ions (OH-).

Furthermore, the pH value of NH4Br is less than 7, indicating that it is an acid. As a result, NH4Br cannot be classified as a base.

The molecular geometry of NH4Br is seen below.

In an aqueous solution, why is NH4Br acidic?

We’ve already established that NH4Br is acidic in nature since it’s an ionic salt of strong acid and weak base. However, the ions that govern the acidity of NH4Br in an aqueous solution are yet unknown.

Let’s try to make sense of this.

Let us first recollect what we learned about dissociation in an aqueous solution.

• A weak acid reacts with a strong conjugate base to generate a strong conjugate base.

• A strong acid reacts with a weak conjugate base to generate a weak conjugate base.

• A weak base reacts with a strong conjugate acid to produce a strong conjugate acid.

• When a strong base reacts with a weak conjugate acid, the result is a weak conjugate acid.

When NH4Br is dissolved in water, it decomposes into ammonium (NH4+) and bromide (Br-) ions.

The following is a representation of the equation:

NH4Br (aq)   —–>   NH4+   +   Br –

Br – is a weak conjugate base of a strong acid (HBr) that lacks the strength to hydrolise further and hence has no effect on the solution’s pH.

The NH4+ ion, on the other hand, is the strong conjugate acid of the weak base NH3. It continues to hydrolyze in the solution, forming hydronium ions and ammonia.

The equation is as follows:

NH4+ (aqueous) —-> NH3 + H3O+

The acidic character of the NH4Br solution is due to the presence of these hydronium ions.


The table below lists some of the properties of NH4Br:

Molar mass97.94 g/mol
Boiling Point452 °C
Melting Point235 °C
pH< 7
Solubility78.3 g/100 g water at 25 °C
Density2.42 g/cm3 at 25 °C
Vapour Pressure1 mm Hg at 198.3 °C
Refractive index1.712 at 25 °C


• Here are a few examples of how ammonium bromide is used:

• Ammonium Bromide is a chemical that is used to make photographic films, plates, and sheets.

• It’s used to keep wooden items from catching fire.

• Lithography and engraving both employ NH4Br.

• Ammonium bromide is also used in therapeutic compositions by the pharmaceutical industry.

• It’s also a corrosion preventative.

• In photochemical reactions, ammonium bromide is employed.

• It can also be used to precipitate silver salts.


• Ammonium Bromide has an acidic pH. It’s a weak base (HBr) and strong acid (HBr) ionic salt (NH3).

• After dissociation of NH4Br in an aqueous solution, ammonium ions are produced, which then ionise to release proton. The acidity of the solution is caused by this proton.

• Its pH level is less than 7.

• It’s a powerful electrolyte that dissolves in water to form ammonium (NH4+) and bromide (Br-) ions.

I hope this article clarified some of your concerns. If you require any further clarification on any of the chemistry concepts, please let me know in your valued comments.


Read more: Is PCl3 an Ionic or a Covalent Compound?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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