Alkali (Water-Soluble Bases): Properties, Examples, and Industrial Uses
Overview of alkalis—water-soluble bases that raise pH, common examples (NaOH, KOH, Ca(OH)2, ammonia), their reactions, industrial uses and handling and safety considerations.
In chemistry, an alkali is a water-based solution that contains dissolved base and has a pH greater than 7. Such solutions contain hydroxide ions (OH−) or other species that make the solution alkaline.
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Etymology
The word originates from the Arabic term qali, which referred to plant ashes used for cleaning. Historically, those ash solutions produced alkaline liquids useful for washing and soap production.
Chemical meaning
Technically an alkali is any base that is soluble in water. In practice, strong alkalis are often metal hydroxides. When a base dissolves, it increases the concentration of OH− in the solution and raises the pH.
Common examples
- Sodium hydroxide (NaOH) and potassium hydroxide (KOH) — hydroxides of the alkali metals.
- Calcium hydroxide (Ca(OH)2) — a less soluble hydroxide from the alkaline earth metals that still produces an alkaline solution.
- Aqueous ammonia (NH3 in water) — a molecular base that forms an alkaline solution.
Relationship to salts
Neutralization of an alkali by an acid produces water and a salt. Many soluble salts, when dissolved, can also give alkaline solutions if the corresponding acid is weak and the salt hydrolyzes to produce OH−.
Uses and safety
Alkalis are widely used in industries and households: they are important in soap and detergent manufacture (saponification), paper and textile processing, water treatment, and chemical synthesis. Concentrated alkalis are corrosive and can cause chemical burns; appropriate protective measures are required when handling them.
Questions and answers
Q: What is an alkali in chemistry?
A: An alkali in chemistry is an aqueous solution with a pH value of more than 7.
Q: What is the origin of the word 'alkali'?
A: The word 'alkali' comes from the Arabic word 'qali' which means 'from the ashes'.
Q: Why are ashes mixed with water used as cleaning products made of alkali materials?
A: Ashes mixed with water used as cleaning products are made of alkali materials because the word 'alkali' comes from the Arabic 'qali' meaning 'from the ashes'.
Q: What is the opposite of an acid?
A: The opposite of an acid is an alkali.
Q: Can an alkali be neutralized?
A: Yes, an alkali can be neutralized by adding an acid.
Q: What is required for a substance to be considered an alkali?
A: For a substance to be considered an alkali, it needs to be a base that is dissolved in water with a pH value greater than 7.
Q: What type of metals are often used to make the salt of an alkali metal?
A: The salt of an alkali metal is often made using alkali metals.
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AlegsaOnline.com Alkali (Water-Soluble Bases): Properties, Examples, and Industrial Uses Leandro Alegsa
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