Difference Between Alkali and Base

Edited By Team Careers360 | Updated on Jul 02, 2025 04:54 PM IST

It had taken centuries for the theory of acids and bases to take shape. Acids taste sour, and that's why they got their name (the Latin word acidus means sour): they're acidic. On the other hand, bases taste bitter. Arrhenius was the first to classify acids and bases scientifically. However, with time, the definition has changed in order to generalize and incorporate all the acids and bases under a single definition respectively. Alkalis are bases only but can be dissolved in the water. This article discuss about definition of alkali and bases and also the differences between alkali and base.

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Bases

There are three distinct definitions for a base and every certainly considered one among them defines a base in its personal way. These three definitions for a base are as follows

Arrhenius Concept: Any compound which furnishes OH^- ions in its aqueous answer is named as a base. This definition covers all of the hydroxides of alkali metals and alkaline earth metals bases which includes NaOH, Ca (OH)₂ etc. This is a best definition of a base. In trendy bases are the compounds that react with acids to supply salt. This definition covers a number of the bases however leaves out many. So, different definitions of bases have been given via way of means of one-of-a-kind scientists.
Bronsted Lowry Concept: Any compound this is able to accepting a proton i.e., a H⁺ ion is named as a base. By this definition, even H₂O can act as a base as it may gather a proton to shape hydronium ion i.e., H₃O⁺ ion. This definition covers maximum of the bases however nevertheless leaves the various bases due to the fact now no longer all bases extract H⁺. AlCl₃ acts as a Lewis acid however it has no H⁺ to supply. So, bases which react with such acids can’t be defined via way of means of this definition. So, any other definition of a base became given via way of means of Lewis.
Lewis Concept: Any compound that could donate a lone pair or can donate a couple of electrons is named as a base. For instance: NH₃ is a Lewis base. It has a lone pair which it may donate. Lewis base normally extract protons and turn out to be strong which includes NH₃, that acquires a proton to shape NH₄⁺. So, in keeping with this definition any compound, ion or detail which could donate a couple of electrons to the opposite species can act as a base. It may be CuO, ZnO. It is a greater generalized definition. NaOH, and KOH supply OH^- which could donate a couple of electrons. Therefore, Lewis idea covers maximum of the elements of a base.

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What is Alkali?

Alkalis are water soluble bases. In different words, bases which may be dissolved in water to grant OH^- ions are termed as alkali. Alkalis are like a subset of bases. So, we are able to say that “All alkali are bases however all bases aren't alkali”. The time period alkali is particularly used for the hydroxides of alkali metals or alkaline earth metals as they effortlessly dissolve in water to grant OH^- ions. Alkali flips pink litmus blue and are sour to taste. And, pH of a alkali answer is extra than 7.

Examples of alkali:

NaOH, KOH, Be (OH)₂, Ca (OH)₂

Sodium hydroxide (NaOH) – caustic soda

Potassium hydroxide (KOH) – caustic potash

Calcium hydroxide, {Ca (OH)₂ } – limewater

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Difference Between Alkali and Base

In general, people use those phrases interchangeably however there's a primary distinction among the . Alkali metal hydroxides and alkaline earth metal hydrides are classified as alkali metal hydroxides. They do now no longer consist of NH₃. So as in line with this definition, NH₃ isn't an alkali although it is a base. Similarly, there’s some other definition to it which is going this way: The bases which dissolve in water to provide OH^- are alkalis. This definition additionally excludes NH₃. So the distinction lies withinside the truth that alkali is sort of a subset of bases. That’s why we will say, all alkali are bases however now no longer all bases are alkali. The differences between alkali and bases include

Concept

The base is a material that, when dissolved in water, raises the concentration of OH^-ions. Alkalis dissolve easily in water and give a clear solution. It's possible that the solution will have a repulsive odor. However, the amount of water, alkali, and alkali's PH value all play a role. This is one of the main differences between alkali and base.

Characteristics

Both the physical and chemical properties of alkali are the same. They are pliable and easily cut with a knife if desired. They’re made of a material with a low melting point and density. Sodium, potassium, and lithium, for example, have a density that makes them afloat in water.This is another difference between alkali and base.

Uses

Organic tannins, fluorides and other pollutants are removed from water using alkalis. They're utilized to make water's pH more alkaline. Alkali is used to keep the sewage sludge clean and to cut down on odors. To make wastewater more visible, they're employed in manufacturing and mining. This also aids in the removal of phosphate and nitrogen. When it comes to kitchens, table salt (sodium chloride) is an alkali that is used. For example, bases can be found in laxatives, as well as soaps, detergents, and other household cleaners. They are also used to neutralize acidic wastewater as a non-hazardous alkali. Antiperspirant deodorant contains them as well.

Properties

Bases have a harsh flavor and a slick, soapy feel to them. They produce water and salt molecules when they react with acids. All three of these substances can be used to make various types of bases. Alkalis are metals with a silvery hue that are highly reflective and pliable. One electron covers the outside of their shell. Cations arise when an ion is withdrawn. This is also a difference between alkali and base.

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Dissociation in Water

When bases and water are combined, the bases breakdown to produce free hydrogen ions (OH-). Alkalis, on the other hand, react aggressively when coupled with water. As a result of the reaction, hydrogen gas and base (a very alkaline solution) are produced. This is also a difference between alkali and base.

It clear that all alkalis are bases but all bases are not alkalis.

Alkalis Bases

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NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. Are alkali and base the same thing?

The most common ones include metal oxides, hydroxides, carbonates, and molten hydrogen carbonates. Many bases are insoluble, meaning that they don't dissolve in water. For bases, an alkali means something that dissolves easily in water. Base/simple solution and alkaline/intermediate solution are same chemical terms.

2. Why are bases referred to as alkali?

When alkali metals come into contact with water, they produce alkali (basic) and metal oxides as a byproduct of the reaction. Alkali metal oxides are bases that can be dissolved in water to produce an alkaline solution. Reaction with water transforms Group 2 metals into bases that are then found in the Earth's crust as basic oxide cations.

3. What are the purpose of using alkali?

Paper, soap, and detergents are all manufactured using traditional alkalis, such as sodium hydroxide. Alkaline, Ni-Cd, and Ni-MH batteries all employ potassium hydroxide as the electrolyte, and potassium hydroxide is also used in agriculture to turn acid soil more alkaline so that plants may thrive there.

4. What is the meaning of free alkali?

Free caustic al-kali is commonly defined as free NaOH, while total free alkali comprises free caustic al-kali and other alkaline substances other than soap, primarily sodium carbonate and silicate.

5. Which bases are called alkali?

Alkalis are water soluble bases. They have a soapy, sour, and caustic sensation. So, an alkali is like a building's foundation. To give a few examples, there's NaOH, KOH, and others.

6. What is alkaline meaning?/What is alkaline?

Alkaline is the aqueous solution with pH greater than 7.

7. What is the main difference between an alkali and a base?

An alkali is a specific type of base that is soluble in water. All alkalis are bases, but not all bases are alkalis. Bases are substances that can accept protons (H+ ions) or donate hydroxide ions (OH-), while alkalis specifically refer to bases that dissolve in water to produce hydroxide ions.

8. Can you explain why all alkalis are bases, but not all bases are alkalis?

All alkalis are bases because they produce hydroxide ions (OH-) in water, which is a characteristic of bases. However, not all bases are alkalis because some bases are insoluble in water or don't produce hydroxide ions when dissolved. For example, magnesium hydroxide is a base but not an alkali because it's not very soluble in water.

9. How do alkalis and bases differ in their pH values?

Both alkalis and bases have pH values above 7, which is considered basic or alkaline. However, alkalis typically have higher pH values (usually 11-14) because they dissociate completely in water, producing a high concentration of hydroxide ions. Some bases may have lower pH values (8-10) if they don't dissociate as fully or are less soluble.

10. How do bases that are not alkalis behave differently in water?

Bases that are not alkalis may not dissolve readily in water or may not produce a significant concentration of hydroxide ions when dissolved. For example, magnesium hydroxide (milk of magnesia) is a base but not very soluble in water. It forms a suspension rather than a clear solution and doesn't significantly increase the hydroxide ion concentration in water.

11. What is the Arrhenius definition of bases, and how does it relate to alkalis?

The Arrhenius definition states that bases are substances that release hydroxide ions (OH-) in aqueous solutions. This definition directly applies to alkalis, as they are water-soluble bases that produce hydroxide ions. However, this definition is limited and doesn't encompass all bases, which is why broader definitions like Brønsted-Lowry and Lewis are also used in chemistry.

12. What are some common examples of alkalis used in everyday life?

Common alkalis include:

13. Can you explain the concept of conjugate bases and how it relates to alkalis?

A conjugate base is what remains after an acid donates a proton (H+). For alkalis, the conjugate base is typically the hydroxide ion (OH-). For example, when sodium hydroxide (NaOH) dissociates in water, it forms Na+ and OH-. The OH- ion is the conjugate base of water (H2O) and is responsible for the basic properties of the solution.

14. Can you explain the concept of amphiprotic substances and how it relates to alkalis and bases?

Amphiprotic substances can act as both acids and bases, depending on the reaction conditions. Water is a common example. While alkalis are typically not amphiprotic (they're strong bases), some weaker bases can exhibit amphiprotic behavior. For instance, the bicarbonate ion (HCO3-) can act as a base by accepting a proton, or as an acid by donating a proton, depending on the pH of the solution.

15. What is the role of alkalis and bases in buffer solutions?

Both alkalis and bases can be components of buffer solutions, which resist changes in pH when small amounts of acid or base are added. However, strong alkalis are typically not used directly in buffers because they would overwhelm the buffering capacity. Instead, the conjugate bases of weak acids (which may or may not be alkalis) are often used. For example, the acetate ion (CH3COO-) from a weak acid (acetic acid) can act as a base in a buffer solution.

16. What is the role of alkalis and bases in soap making?

Alkalis play a crucial role in soap making through the process of saponification, where they react with fats or oils to produce soap. Strong alkalis like sodium hydroxide (for hard soaps) or potassium hydroxide (for soft soaps) are typically used. While other bases could theoretically be used, alkalis are preferred due to their strong basicity, solubility, and ability to completely saponify fats.

17. Can you explain the concept of Lux-Flood bases and how it relates to alkalis?

The Lux-Flood theory defines bases as oxide ion (O2-) donors. This definition is particularly useful in high-temperature inorganic chemistry and molten salt systems. While this concept doesn't directly relate to the aqueous behavior of alkalis, it provides a broader understanding of basic behavior. Some alkalis, like sodium oxide (Na2O), can act as Lux-Flood bases by donating oxide ions in appropriate conditions.

18. Can you explain the concept of superbasicity and how it relates to alkalis?

Superbases are extremely strong bases that are more powerful than the hydroxide ion. While many alkalis are strong bases, not all reach the level of superbasicity. Some non-alkali compounds, like organolithium compounds or Grignard reagents, can exhibit superbasic properties. However, some alkali metal compounds, like sodium hydride (NaH) or n-butyllithium, are considered superbases due to their extreme basicity.

19. What is the importance of alkalis and bases in the production of fertilizers?

Both alkalis and bases are important in fertilizer production, but they serve different roles. Strong alkalis like sodium hydroxide are used in the production of phosphate fertilizers by treating phosphate rock. Ammonia, a non-alkali base, is crucial in the production of nitrogen fertilizers. The choice between alkalis and other bases in fertilizer production depends on the specific chemical processes and the desired end products.

20. Can you explain the concept of proton sponges and how it relates to alkalis and bases?

Proton sponges are extremely strong bases with a high affinity for protons. While some alkalis are strong bases, proton sponges are typically organic compounds with specific structural features that

21. How do alkalis and bases differ in their reaction with acids?

Both alkalis and bases react with acids in neutralization reactions. However, alkalis tend to react more vigorously and completely with acids because they dissociate fully in water, providing a higher concentration of hydroxide ions. Non-alkali bases may react more slowly or incompletely due to lower solubility or weaker dissociation.

22. How do alkalis and bases differ in their electrical conductivity?

Alkalis generally have higher electrical conductivity in aqueous solutions compared to non-alkali bases. This is because alkalis dissociate completely in water, producing a high concentration of ions (like Na+ and OH-) that can carry electric current. Non-alkali bases may have lower conductivity if they don't dissociate as fully or are less soluble.

23. What role do alkalis play in the pH scale compared to other bases?

Alkalis are at the extreme end of the pH scale, typically with pH values between 11 and 14. They have a more pronounced effect on pH than weaker bases because they dissociate completely in water, releasing a high concentration of hydroxide ions. Other bases may have a more moderate effect on pH, falling in the 8-10 range.

24. How do alkalis and bases differ in their reaction with metals?

Both alkalis and bases can react with certain metals, but alkalis tend to be more reactive. Strong alkalis like sodium hydroxide can react with amphoteric metals (e.g., aluminum, zinc) to produce hydrogen gas and a metal hydroxide or salt. Non-alkali bases may react more slowly or not at all with some metals due to their lower solubility or weaker basic strength.

25. What is the difference between strong and weak bases, and how does this relate to alkalis?

Strong bases dissociate completely in water, while weak bases only partially dissociate. Most common alkalis (like NaOH and KOH) are strong bases, which is why they have such a significant effect on pH and reactivity. However, not all strong bases are alkalis (e.g., barium hydroxide is a strong base but less soluble), and some alkalis can be weak bases (e.g., ammonia solution).

26. How do alkalis and bases differ in their effect on indicators?

Both alkalis and bases cause color changes in indicators, but alkalis often produce more dramatic and consistent changes due to their higher pH and complete dissociation. For example, phenolphthalein turns bright pink in alkali solutions but may show a lighter pink or no change in some weaker, non-alkali base solutions.

27. Can you explain the concept of alkalinity and how it differs from basicity?

Alkalinity refers to the capacity of a solution to neutralize acids, typically measured by the concentration of carbonate, bicarbonate, and hydroxide ions. Basicity, on the other hand, refers to the ability of a substance to accept protons or donate hydroxide ions. All alkalis contribute to alkalinity, but not all substances that contribute to alkalinity are alkalis (e.g., carbonates).

28. How do alkalis and bases differ in their reaction with organic compounds?

Alkalis, being stronger and more reactive, can cause more significant changes to organic compounds. They can hydrolyze esters, saponify fats (make soap), and deprotonate weak acids more readily than non-alkali bases. Some organic reactions, like the aldol condensation, specifically require strong alkalis rather than weaker bases.

29. What is the role of water in defining alkalis versus bases?

Water plays a crucial role in defining alkalis. By definition, alkalis must be water-soluble bases. Water acts as the solvent that allows alkalis to dissociate and produce hydroxide ions. Bases, in general, don't necessarily need to interact with water to exhibit their basic properties, as seen in the broader Brønsted-Lowry and Lewis definitions of bases.

30. How do alkalis and bases differ in their corrosive properties?

Alkalis are generally more corrosive than non-alkali bases due to their higher pH and complete dissociation in water. Strong alkalis like sodium hydroxide can cause severe chemical burns and can dissolve certain materials (like aluminum) more readily than weaker bases. Non-alkali bases may be less corrosive, depending on their strength and solubility.

31. How do alkalis and bases differ in their reaction with carbon dioxide?

Both alkalis and bases can react with carbon dioxide, but alkalis tend to react more vigorously. Alkalis like sodium hydroxide readily absorb CO2 from the air, forming carbonates (e.g., Na2CO3). This reaction is often used in CO2 scrubbers. Non-alkali bases may also react with CO2, but the reaction may be slower or less complete, depending on the base's strength and solubility.

32. What is the significance of the hydroxide ion in alkalis compared to other bases?

The hydroxide ion (OH-) is central to the definition and behavior of alkalis. Alkalis produce a high concentration of hydroxide ions when dissolved in water, which is responsible for their high pH and strong basic properties. Other bases may not necessarily produce hydroxide ions (e.g., ammonia forms NH4+ and OH- indirectly through reaction with water) or may produce them in lower concentrations.

33. How do alkalis and bases differ in their ability to accept protons?

While both alkalis and bases can accept protons (H+), alkalis typically do so more readily and completely. This is because alkalis dissociate fully in water, producing a high concentration of hydroxide ions that can quickly accept protons. Non-alkali bases may accept protons less efficiently, especially if they're weak bases or have limited solubility.

34. Can you explain the concept of Lewis bases and how it relates to alkalis?

Lewis bases are defined as electron pair donors. While this definition encompasses alkalis (the hydroxide ion can donate an electron pair), it's broader and includes bases that don't necessarily produce hydroxide ions. For example, ammonia is a Lewis base because it can donate an electron pair, but it's not an alkali in its pure form (though its aqueous solution is weakly alkaline).

35. How do alkalis and bases differ in their effect on the human body?

Both alkalis and bases can be harmful to the human body, but alkalis are generally more dangerous due to their higher pH and corrosive nature. Strong alkalis can cause severe chemical burns and tissue damage. They can saponify fats in the body, leading to deep tissue destruction. Non-alkali bases may also be harmful but are often less severe unless they have other toxic properties.

36. How do alkalis and bases differ in their reaction with amphoteric substances?

Amphoteric substances can react as either an acid or a base. Alkalis, being stronger bases, tend to react more vigorously with the acidic nature of amphoteric substances. For example, strong alkalis like NaOH can dissolve amphoteric metals like aluminum or zinc. Weaker, non-alkali bases might not react as readily or completely with amphoteric substances.

37. Can you explain the concept of Brønsted-Lowry bases and how it relates to alkalis?

The Brønsted-Lowry definition describes bases as proton (H+) acceptors. This definition encompasses alkalis, as they accept protons through their hydroxide ions. However, it also includes bases that don't produce hydroxide ions, like ammonia (NH3), which accepts a proton to form NH4+. This broader definition helps explain the behavior of bases in non-aqueous solutions and gas-phase reactions.

38. How do alkalis and bases differ in their effect on protein structures?

Both alkalis and bases can denature proteins, but alkalis are generally more effective due to their higher pH and reactivity. Strong alkalis can break down proteins by hydrolyzing peptide bonds and disrupting hydrogen bonds and other interactions that maintain protein structure. They can also saponify any fats associated with the protein. Weaker, non-alkali bases may have a less dramatic effect on protein structure.

39. How do alkalis and bases differ in their reaction with halogens?

Both alkalis and bases can react with halogens, but alkalis generally react more vigorously. For example, alkalis react with chlorine to produce hypochlorite ions (ClO-) and halide ions, a reaction used in producing bleach. Non-alkali bases may also react with halogens, but the reactions might be slower or produce different products depending on the specific base and conditions.

40. How do alkalis and bases differ in their ability to form coordination compounds?

Both alkalis and bases can form coordination compounds, but their behavior differs. Alkalis typically form simple ionic compounds with metal ions. For example, sodium hydroxide can form sodium aluminate (NaAlO2) with aluminum. Non-alkali bases, especially those with lone pairs of electrons (like ammonia), can form more complex coordination compounds by donating electron pairs to metal ions, acting as ligands.

41. What is the significance of alkalis and bases in the context of acid-base titrations?

Both alkalis and bases can be used in acid-base titrations, but alkalis are often preferred, especially for standardization. Strong alkalis like sodium hydroxide provide sharp endpoints due to their complete dissociation and high pH change near the equivalence point. Weaker bases or non-alkali bases may provide less distinct endpoints or require different indicators, making them less ideal for certain titrations.

42. How do alkalis and bases differ in their effect on glass?

Alkalis, especially strong ones like sodium hydroxide, can etch or dissolve glass over time. This is due to their ability to break down the silicate network in glass. Non-alkali bases generally have less effect on glass, unless they're particularly strong or used at high concentrations. This is why strong alkali solutions are often stored in plastic containers rather than glass.

43. How do alkalis and bases differ in their role in biological systems?

Both alkalis and bases play important roles in biological systems, but their effects can differ. Strong alkalis are generally not found in living organisms due to their corrosive nature. However, weaker bases and alkalis, like bicarbonate ions, play crucial roles in maintaining pH balance in blood and other bodily fluids. Some non-alkali bases, like amino groups in proteins, are fundamental to many biological processes.

44. How do alkalis and bases differ in their reaction with transition metal complexes?

Both alkalis and bases can react with transition metal complexes, but their effects can differ. Strong alkalis can often displace ligands in complexes, forming hydroxo complexes or precipitating metal hydroxides. Non-alkali bases, especially those that can act as ligands (like ammonia), may form new complexes by replacing existing ligands. The specific reaction depends on the strength of the base, the nature of the complex, and the reaction conditions.