Weak Base - Classifications, Examples, Uses, FAQs

Edited By Team Careers360 | Updated on Jul 01, 2022 03:36 PM IST

Classification on The Basis of Strength:

Strong Base: A strong base is one that totally dissolves in water. For example, KOH, NaOH, and so forth. Weak bases: This substance does not entirely dissolve in water. For example, NH₃, Zn(OH)₂ When dissolved in solutions, weak bases are described as basic compounds that do not entirely breakdown into their constituent ions. As a result, when the weak bases is dissolved in a solution, a portion of it dissociates into hydroxide anions and the appropriate conjugate acid, while rest stays undissociated inside solution. It's vital to remember that weak bases conjugate acid is usually always weak acid. Similarly, a weak acid and weak base's conjugate base will operate as a weak bases.

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Classification on The Basis of Strength:
Weak Bases Examples
Uses of Weak Base

The following form of equilibrium occurs when a weak bases is dissolved in water:

B + H₂O ⇌ BH⁺ + OH^–

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Weak Bases Examples

Ammonia (NH₃)

The chemical compound ammonia has the formula NH₃. It's a weak bases that exists as a colourless gas under ordinary temperature and pressure settings. The unpleasant odour of this gas is well-known. It's worth noting, though, that only small portion of dissolved ammonia dissociates into these ions.

Trimethylamine (N(CH3)3)

TMA stands for trimethylamine, which is weak bases with molecular formula N(CH₃)₃. It can also be made by combining paraformaldehyde along with ammonium chloride in a process.

Pyridine (C5H5N)

Pyridine is pyridine-like organic molecule with formula C₅H₅N. This chemical compound is weak bases with heterocyclic structure. Pyridine has a structure similar to benzene, with exception that one of the methine groups is substituted with single nitrogen atom.

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Aniline

Organic molecules with the chemical formula C₆H₅NH₂ are known as anilines. It's used to make rubber chemicals and items including automobile tyres, balloons, and gloves in the rubber industry. It is a weak bases that generates an anilinium ion when treated with strong acids. It's utilised in pesticides and fungicides in agriculture, as well as agricultural chemicals, synthetic colours, antioxidants, herbicides, varnishes, and explosives.

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Example of Weak Acid

Formic Acid

One of the most basic carboxylic acids is formic acid, commonly known as methanoic acid. HCOOH or CH₂O₂ is the chemical formula for this substance. Formic acid is a weak acid that is found naturally inside the bodies of some ants. Formic acid is a colourless liquid that exists under typical temperature and pressure conditions (which sometimes evolves fumes).

Formic acid is reported to have a strong and penetrating unpleasant odour when it is liquid. Several additional organic solvents, such as acetone, glycerol, ethanol, and methanol, create miscible mixes with formic acid. Furthermore, it is known that this molecule is somewhat soluble in aromatic chemicals like benzene and toluene.

Uses of Weak Base

Ammonium Hydroxide

Fertilizers, rayon, plastics, and colours are all made from it.

In a chemical laboratory, it is employed as a reagent.

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NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. What are the examples of weak bases?

Weak base examples: Ammonia; Aluminum hydroxide; Lead hydroxide; Ferric hydroxide etc.

2. Explain ionization of Weak base

An arrow pointing from left to right represents the reaction sign for a strong base ionising in water. The reaction arrow for a weak bases ionising in water, on the other hand, is a double arrow, indicating that both the forward and reverse reactions are in equilibrium. The weak bases, its conjugate acid, and the hydroxide ion are all present in the aqueous solution at equilibrium circumstances.

For a weak bases, we can determine the equilibrium constant Kb.

Let's look at the ionisation of a weak bases, MOH, in water to better comprehend this concept:

MOH (aq) ⇌ M⁺(aq) + OH^-(aq)

If the initial concentration of MOH is c mole/lit and the degree of dissociation is indicated as α, MOH will have (c - cα) moles/lit at equilibrium, whereas M^- and OH^- will each have (cα) moles/lit.

As a result, the Kb for the given equation is:

Kb= [M⁺] [OH^-][MOH][M⁺][OH^-][MOH]

Or, Kb = cα²/ (1- α)

The concentration of each component is indicated by the square brackets above. The weaker the base , the more the balance is concentrated on the left side. Similarly, the stronger the base is, the higher the equilibrium concentration on the right side. According to the preceding equation, Kb is directly proportional to OH^- concentration, implying that bases with higher Kb values are more powerful than those with lower Kb values.

3. Is water a weak bases?

Pure water does, in fact, act as a weak bases. In reality, pure water is a weak acid as well as a weak bases. This is because a little amount of water dissociates into protons and hydroxide anions, forming hydronium ions and hydroxide ions with the remaining water molecules.

4. List 3 examples of weak base

Below are three common instances of weak base.

Ammonia
Pyridine
Methylamine

5. State the differences between Strong and Weak bases

The most significant differences between a strong and a weak bases are-

During an acid reaction, strong bases totally ionise, whereas weak base only partially ionise.
Strong bases are more likely to receive protons, whereas weak base are less likely to accept protons.
Strong bases have a pH between 10 and 14 on a pH scale, while weak base have a pH between 7.3 and 10.
Strong bases have a high reactivity, whereas weak base have a lower reactivity.
Strong bases have high pKb values, whereas weak base have low pKb values.
Strong bases are good conductors of electricity, whereas weak base are bad conductors.
Strong bases have large equilibrium constants, while weak base have low ones; on the equilibrium scale, as the acid becomes weaker, the value swings to the left.

Weak base are not excellent electrolytes, whereas strong bases are.