An alkali is a chemical compound that is a type of base. When dipped in water, it becomes a solution.
When an alkali is added to any other acid, the PH increases. In contrast, when an acid is added to an alkali, the PH decreases due to the removal of the alkali.
Key Takeaways
- 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.
- All alkalis are bases, but not all are alkalis since some do not dissolve in water or produce hydroxide ions.
- 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.
Comparison Table
| Parameter of Comparison | Alkali | Base |
|---|---|---|
| Compounds | It consists of carbonates and hydroxides of alkali metals | Any compound that consists of a hydroxide class can be free. Or compounds that accept protons or lone electron pairs. |
| Definition | Alkali refers to metals found in group 1 of the periodic table. | A base is a compound that consists of hydroxide ions or lone electron pairs. The electron pairs can be transferred to another chemical species. |
| Ionic Compound Formation | Alkali forms ionic compounds by forming cations from alkali metals | Bases can either form covalent or ionic compounds |
| Chemical category | Belongs to group 1 metals or their ionic compounds | Their chemical category is any compound, either ionic or covalent |
| Strength | The strength of alkali can be strong or weak depending on the nature and concentration of the ionic salt composing it. | The strength of the base depends on the concentration of hydroxide ions. |
What is Alkali?
Alkalis are chemical compounds. They contain one electron in their outermost layer of electrons.
Getting rid of the outermost electron from an alkali metal requires less energy. Ionization energy is required to remove an electron from the outer shell of an alkali.
They are soft metals as a result of metallic bonding. As such, you can cut them using a knife. Still, they have low boiling and melting points.
Alkalis are reactive metals. They are kept in solutions such as kerosene to prevent them from reacting with the atmosphere.
When burning with oxygen, they form coloured flames.
The density of alkali metals is lower compared to other metals. They are good conductors of heat and electricity.
What is Base?
A base is a substance that is used to neutralize the acid. They may or may not be soluble in water. Those that dissolve in water are known as alkalis.
Bases are bitter to taste, a feature of all bases. And just like acids, they can be strong or weak. Those that are strong can burn the skin and are very corrosive.
NaOH is an example of a strong base, while NH3 is an example of a weak base. Bases are slippery in nature but bitter in taste.
When they react with acid, they produce water and salt molecules.
Main Differences Between Alkali and Base
Concept
The base is a substance that will increase OH-ion concentration when dissolved in water. When an alkali is dissolved in water, the solution produced is transparent.
The solution can also have an awful smell. But again, it depends on the amount of water, an alkali, and the PH value of the alkali.
Physical Characteristics
Alkali’s physical and chemical characteristics are the same. They are soft and can be cut using a knife. They have low melting points and low densities. For instance, sodium, potassium, and lithium are low to float on water.
Bases are bitter when you taste them. Apart from ammonia, the rest are odourless. They are slippery and react with fats and oils.
Uses
Alkalis soften water and remove organic tannins, fluorides, and other impurities. They are used to neutralize the pH levels of water. Alkali is applied to maintain the sewage sludge and reduce odour.
They are used in industrial applications and mining operations to wastewater to help improve visibility. This also helps to remove phosphorus and nitrogen.
Sodium chloride, an alkali, is used in kitchens as table salt. Bases are used in gastric medicine, soaps, detergents, and cleansers.
They are also used as a non-hazardous alkali to neutralize acidic wastewater. Furthermore, they are used in antiperspirant and armpit deodorant.
Properties
Bases have a bitter taste and a slippery feeling like that of soap. They react with acids to produce water and salt molecules. Ammonia, baking soda, and caustic soda are the standard bases.
Alkalis are silvery colour metals that are shiny and soft. Their outside shell is covered by one electron. When removed, they form +1 cations.
Dissociation when mixed with water
When mixed with water, bases dissociate to give free hydrogen ions (OH-). On the other hand, Alkalis react violently when mixed with water. The reaction produces hydrogen gas and a strongly alkaline solution known as a base.
- https://vtechworks.lib.vt.edu/bitstream/handle/10919/54192/LD5655.V856_1989.H373.pdf?sequence=1
- https://pubs.rsc.org/en/content/articlehtml/1995/c3/c39950001005
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
