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Alkali vs. Acid: What's the Difference?

Edited by Harlon Moss || By Janet White || Published on December 12, 2023
Alkalis are basic, often soluble in water, and have a pH greater than 7, whereas acids are substances that release hydrogen ions in water and have a pH less than 7.

Key Differences

Alkali substances, typically found in bases like sodium hydroxide, have properties like feeling slippery and turning litmus paper blue. While, acids, like hydrochloric acid, taste sour and turn litmus paper red. Both are key in chemical reactions but with opposite characteristics.
Alkalis are composed of alkali metals and hydroxide ions, effective in neutralizing acids. However, acids, composed of hydrogen and non-metal ions, react with metals and carbonates, often producing carbon dioxide.
The pH scale measures how acidic or basic a substance is. Alkalis have a high pH, above 7, indicating a basic nature. In contrast, acids have a low pH, below 7, signifying their acidic properties.
Alkalis react with acids in neutralization reactions, forming water and a salt. Whereasd, acids can react vigorously with metals, releasing hydrogen gas and forming salts.
Alkalis are used in cleaning agents and soaps due to their ability to dissolve grease. Acids have diverse uses, including in batteries (sulfuric acid), food (citric acid), and industry (hydrochloric acid).

Comparison Chart

PH Value

Greater than 7 (basic)
Less than 7 (acidic)

Litmus Test

Turns litmus paper blue
Turns litmus paper red


Usually tasteless or bitter


Reacts with acids to form salt and water
Reacts with bases, metals, and carbonates

Common Examples

Baking soda (sodium bicarbonate), soap
Vinegar (acetic acid), lemon juice (citric acid)

Alkali and Acid Definitions


Any substance having basic (as opposed to acidic) properties.
Baking soda, a common alkali, is often used in baking.


A substance that increases the hydrogen ion concentration of a solution.
Lemon juice, an acid, adds a sour flavor to dishes.


A substance with a pH higher than 7.
Ammonia, a strong alkali, is used in many household cleaners.


A molecule or other entity that can donate a proton or accept an electron pair in reactions.
Hydrochloric acid, a strong acid, is used in industrial cleaning.


A chemical compound that neutralizes or effervesces with acids.
Soap, an alkali, is used for cleaning as it reacts with oil and grease.


A sour-tasting material typically corrosive to metals.
Vinegar, an acid, is commonly used in cooking and cleaning.


A soluble salt obtained from the ashes of plants and consisting largely of potassium or sodium carbonate.
Potash, derived from plant ashes, is an ancient form of alkali.


A substance with a pH less than 7.
Citric acid, found in citrus fruits, is known for its tangy taste.


A base that dissolves in water.
Sodium hydroxide, an alkali, is used in drain cleaners.


A chemical substance that neutralizes alkalis.
Sulfuric acid, a potent acid, is used in car batteries.


A carbonate or hydroxide of an alkali metal, the aqueous solution of which is bitter, slippery, caustic, and characteristically basic in reactions.


Any of a class of substances whose aqueous solutions are characterized by a sour taste, the ability to turn blue litmus red, and the ability to react with bases and certain metals to form salts.


Any of various soluble mineral salts found in natural water and arid soils.


A substance that yields hydrogen ions when dissolved in water.


Alkali metal.


A substance having highly basic properties; a strong base.


(chemistry) One of a class of caustic bases, such as soda, soda ash, caustic soda, potash, ammonia, and lithia, whose distinguishing characteristics are dissolving in alcohol and water, uniting with oils and fats to form soap, neutralizing and forming salts with acids, turning to brown several vegetable yellows, and changing reddened litmus to blue.


(Western United States) Soluble mineral matter, other than common salt, contained in soils of natural waters.


Soda ash; caustic soda, caustic potash, etc.


One of a class of caustic bases, such as soda, potash, ammonia, and lithia, whose distinguishing peculiarities are solubility in alcohol and water, uniting with oils and fats to form soap, neutralizing and forming salts with acids, turning to brown several vegetable yellows, and changing reddened litmus to blue.


Soluble mineral matter, other than common salt, contained in soils of natural waters.


Any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water;
Bases include oxides and hydroxides of metals and ammonia


A mixture of soluble salts found in arid soils and some bodies of water; detrimental to agriculture


Can acids and alkalis be harmful?

Yes, both can be corrosive and harmful, especially in high concentrations.

What is an alkali?

An alkali is a substance that is basic, with a pH greater than 7, often soluble in water.

What is a common household alkali?

Baking soda is a common household alkali.

Are alkalis always safe to touch?

No, some alkalis can be caustic and harmful to skin.

Do acids have a common taste?

Yes, acids typically taste sour.

How is pH related to acids and alkalis?

pH measures the acidity or basicity; acids have low pH, and alkalis have high pH.

What is a common use of acids?

Acids are commonly used in food, like citric acid in lemons, and in cleaning products.

Are all acids dangerous?

Not all; for example, vinegar and citric acid are commonly used and safe in low concentrations.

What is an acid?

An acid is a substance that releases hydrogen ions in water and has a pH less than 7.

How do alkalis react with acids?

Alkalis react with acids to form salt and water, a reaction known as neutralization.

Can alkalis conduct electricity?

Yes, when dissolved in water, alkalis can conduct electricity.

Are acids typically liquid?

Many acids are liquid, but some, like citric acid, can be solid.

What are some industrial uses of acids?

Acids are used in manufacturing, cleaning, and in batteries.

Are there strong and weak alkalis?

Yes, the strength varies based on their ability to dissociate in water.

Can alkalis be found in food?

Yes, some foods, like certain vegetables, have alkaline properties.

What is a natural source of acid?

Citrus fruits like lemons and oranges are natural sources of citric acid.

Can acids change the color of indicators?

Yes, acids can change the color of indicators like litmus paper to red.

Can alkalis neutralize acids?

Yes, alkalis can neutralize acids, often used in antacids.

What happens when alkalis are mixed with water?

Alkalis often dissolve, forming basic solutions.

Is it safe to mix acids and alkalis?

Care should be taken as the reaction can be vigorous and produce heat.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.

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