Alkali vs Base: Difference and Comparison

An alkali is a soluble hydroxide that releases OH- ions in water, while a base is a broader term referring to substances that can accept protons (H+) or donate electron pairs. All alkalis are bases, but not all bases are alkalis. Bases include substances like metal oxides and ammonia.

Key Takeaways

1. Alkalis are a subset of bases that dissolve in water, producing hydroxide ions (OH-) and increasing the pH of the solution. In contrast, bases are substances that can accept hydrogen ions (H+) in a chemical reaction.
2. All alkalis are bases, but not all are alkalis since some do not dissolve in water or produce hydroxide ions.
3. Examples of alkalis include sodium hydroxide (NaOH) and potassium hydroxide (KOH), while examples of non-alkaline bases include ammonia (NH3) and calcium carbonate (CaCO3).

Alkali vs Base

An alkali is a base that dissolves in water and has a pH greater than 7.0. Examples include sodium hydroxide and potassium hydroxide. A base is a substance that accepts protons with a pH greater than 7.0. Not all bases are alkali; for example, ammonia (NH3) is a base but not an alkali.

Alkali metals are soft, shiny, and not very heavy. They have a weak metallic bond, which is why they are soft. They can easily be sliced into two using a knife.

A base is a substance used to neutralize acids. Metal oxides and metal hydroxides are bases that form neutral products with acids.

Bases are slippery and bitter when you taste them.

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Comparison Table

Feature	Alkali	Base
Definition	A soluble ionic salt of an alkali metal (group 1) characterized by high pH and soapy feel	Any substance that can accept protons or donate electron pairs, characterized by high pH
Examples	NaOH (sodium hydroxide), KOH (potassium hydroxide), Ca(OH)2 (calcium hydroxide)	Ammonia (NH3), Barium hydroxide (Ba(OH)2), Sodium carbonate (Na2CO3)
Solubility in water	Very soluble	Can be soluble or insoluble in water
Reactivity	Highly reactive, can corrode skin and materials	Varied reactivity depending on base, some strong bases are corrosive
Taste	Bitter and soapy	Can vary, some tastes bitter, others pungent or metallic
pH	Greater than 7	Greater than 7, but range can vary (stronger bases have higher pH)
Environmental impact	Can be harmful to the environment and aquatic life due to high pH	Impact depends on specific base, some are harmful, others not
Industrial applications	Soap making, cleaning products, paper production, textile processing	Agriculture, fertilizers, construction materials, medicine
Biological role	Involved in maintaining pH balance in cells and body fluids	Essential for many biochemical reactions

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What is Alkali?

Alkali refers to a class of chemical compounds that are soluble hydroxides of alkali metals. These metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Alkalis are characterized by their ability to release hydroxide ions (OH-) when dissolved in water, making the solution alkaline.

Properties of Alkalis

1. Solubility: Alkalis are soluble in water, and the degree of solubility increases down the alkali metal group in the periodic table.
2. pH Level: Alkali solutions have pH values greater than 7, indicating their basic nature. The higher the concentration of hydroxide ions, the more alkaline the solution.
3. Corrosive Nature: Concentrated alkali solutions can be corrosive and should be handled with care.
4. Reaction with Acids: Alkalis neutralize acids through a chemical reaction, forming water and a salt. This process is known as neutralization.

Sources of Alkalis

1. Natural Deposits: Some minerals and ores contain alkali compounds. For example, sodium hydroxide can be derived from sodium carbonate found in the mineral trona.
2. Synthetic Production: Alkalis can be synthesized through chemical processes. For instance, sodium hydroxide is commonly produced through the electrolysis of sodium chloride (table salt).
3. Biological Processes: Alkalis are involved in various biological processes, such as the regulation of pH in living organisms.

Common Alkali Compounds

1. Sodium Hydroxide (NaOH): Widely used in industries for processes like soap making and as a strong base in chemical reactions.
2. Potassium Hydroxide (KOH): Commonly used in the production of potassium salts and as an electrolyte in alkaline batteries.
3. Lithium Hydroxide (LiOH): Employed in the manufacture of lithium-based products and as a CO2 scrubber in spacecraft.

 

What is Base?

A base, in chemistry, refers to a substance capable of accepting protons (H+) or donating electron pairs. Bases can be classified into two main types: Arrhenius bases, which release hydroxide ions (OH-) in water, and Bronsted-Lowry bases, which can accept protons in chemical reactions.

Types of Bases

1. Arrhenius Bases: These are substances that, when dissolved in water, release hydroxide ions (OH-). Common examples include alkali metal hydroxides like sodium hydroxide (NaOH) and potassium hydroxide (KOH).
2. Bronsted-Lowry Bases: In the Bronsted-Lowry theory, bases are defined as substances capable of accepting protons (H+) during chemical reactions. This broader definition includes substances that do not necessarily contain hydroxide ions.

Properties of Bases

1. pH Level: Bases have pH values greater than 7, indicating their alkaline nature. The higher the pH, the stronger the base.
2. Taste and Feel: Some bases, such as sodium hydroxide, are caustic and have a soapy or bitter taste. They can also feel slippery when touched.
3. Reaction with Acids: Bases neutralize acids through a chemical reaction known as neutralization. The result is the formation of water and a salt.
4. Amphoteric Nature: Some substances, like water and certain metal oxides, can act as both acids and bases depending on the reaction. This property is termed amphoterism.

Sources and Applications of Bases

1. Alkali Metal Bases: Derived from alkali metals, these bases find applications in industries, such as the production of soap, detergents, and various chemicals.
2. Metal Oxides: Compounds like calcium oxide (CaO) and magnesium oxide (MgO) are metal oxides that exhibit basic properties.
3. Ammonia (NH3): An example of a Bronsted-Lowry base, ammonia is commonly used in household cleaning products and as a refrigerant.
4. Biological Significance: Bases are essential in biological systems, contributing to the regulation of pH levels in living organisms.

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Main Differences Between Alkali and Base

• Definition:
  • Alkali: Soluble hydroxides of alkali metals (Li, Na, K, Rb, Cs, Fr) releasing OH- ions in water.
  • Base: A broader term referring to substances capable of accepting protons (H+) or donating electron pairs; includes hydroxides, oxides, and substances with Bronsted-Lowry basic properties.
• Membership:
  • All alkalis are bases, but not all bases are alkalis.
  • Bases encompass a wider range of compounds beyond alkali metal hydroxides.
• Examples:
  • Alkalis: Sodium hydroxide (NaOH), potassium hydroxide (KOH).
  • Bases: Metal oxides (e.g., calcium oxide, CaO), ammonia (NH3).
• Release of Hydroxide Ions:
  • Alkalis specifically release OH- ions in water.
  • Bases may or may not release OH- ions, depending on the type (Arrhenius or Bronsted-Lowry).
• Application:
  • Alkalis find applications in industries like soap-making and as strong bases in chemical processes.
  • Bases have diverse applications, ranging from cleaning products (ammonia) to the regulation of pH in biological systems.

References

1. https://vtechworks.lib.vt.edu/bitstream/handle/10919/54192/LD5655.V856_1989.H373.pdf?sequence=1
2. https://pubs.rsc.org/en/content/articlehtml/1995/c3/c39950001005

Last Updated : 11 February, 2024