Preparation of Bases

Preparation of Bases: Chemical compounds are divided into three different types of nature, i.e., acid, base and neutral substances. Bases are chemical substances that are bitter in taste, soapy to touch and turns red litmus solution or litmus paper to blue. We use many bases in our daily life, such as soaps, antacids for relieving acidity in the stomach, toothpaste for cleaning our teeth, and many more. Soaps are slippery to touch because they are made up of bases.

Toothpaste is also made up of bases as it can react with the acidic cavities of the mouth. Similarly, antacids like Eno or milk of magnesia are bases, and they neutralise the increased acidic level in the stomach. In chemical laboratories, substances that convert red litmus blue are known as bases and substances that convert blue litmus red are known as acids. Compounds that release hydroxyl ions in the aqueous solution are known as bases, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, and many more.

What is a Base?

A base is a chemical substance that donates electrons, accepts protons, or releases hydroxide \(\left( {{\rm{O}}{{\rm{H}}^ – }} \right)\) ions in the aqueous solution. Examples of bases include alkali metal hydroxides like sodium hydroxide, potassium hydroxide, etc., alkaline earth metal hydroxides, calcium hydroxide, magnesium hydroxide, etc., and soap. 

Bases have certain characteristic features that help to identify them. Some of them are:

• They are slippery to the touch (e.g., soap).
• They are bitter in taste.
• Bases react with acids to form salts and catalyse certain reactions. 

Based on different concepts, bases can be defined as under:

1. According to the Arrhenius theory of base, it is a chemical species that produces a hydroxide ion \(\left( {{\rm{O}}{{\rm{H}}^ – }} \right)\) in its solution. 
2. The Bronsted-Lowry theory defines a base as a proton acceptor.
3. Lewis Base is a compound or ionic species which can donate a lone pair of electrons to an acceptor compound.

Types of Bases

According to their degree of dissociation in aqueous solution and reactivity, Bases are classified as under:

1. Strong Base – A base that completely dissociates into its ions in water or is a compound that is capable of removing a proton \(\left( {{{\rm{H}}^ + }} \right)\) from a very weak acid is known as a strong base. Some examples of strong bases include sodium hydroxide \(\left( {{\rm{NaOH}}} \right)\) and potassium hydroxide \(\left( {{\rm{KOH}}} \right)\), etc.
2. Weak Base – A base that incompletely dissociates in water is known as a weak base. The aqueous solution of this type of base includes both the weak base and its conjugate acid.

3. Superbase – A superbase deprotonates better than a strong base. Such bases have very weak conjugate acids and are formed by mixing an alkali metal with its conjugate acid. Since a superbase is a stronger base than the hydroxide ion; it cannot remain in an aqueous solution. Some examples of superbase include sodium hydride \(\left( {{\rm{NaH}}} \right)\), ortho-diethynylbenzene dianion \({\left( {{{\rm{C}}{\rm{6}}}{{\rm{H}}{\rm{4}}}{{\left( {{{\rm{C}}{\rm{2}}}} \right)}{\rm{2}}}} \right)^{{\rm{2 – }}}}\).

4. Neutral Base – A base that forms a bond with a neutral acid in such a manner that the acid and base share an electron pair from the base is known as a neutral base.

5. Solid Base – A solid base is active in solid-state. Such as silicon dioxide \({\rm{(Si}}{{\rm{O}}_{\rm{2}}}{\rm{)}}\) and \({{\rm{NaOH}}}\) mounted on alumina is a solid base. Such bases are used in anion exchange resins or for reactions with gaseous acids.

Properties of Base

Physical properties of base:

1. Aqueous base solution is a good conductor of electricity as molten bases dissociate into ions.
2. Strong and concentrated bases are caustic in nature as they react vigorously with acids and organic matters.
3. A base turns red litmus paper blue, methyl orange to yellow, and phenolphthalein to pink. Bromothymol blue remains blue in the presence of a base. These indicators are used to detect the presence of a base in a solution.
4. The \({\rm{pH}}\) of a basic solution is greater than \(7\). 
5. Bases are bitter in taste.

Chemical properties of base:

An acid and a base react with each other to form salt and water, and this chemical reaction is known as a neutralisation reaction. In neutralisation, an acid and a base in an aqueous state produce an aqueous solution of salt and water. If the salt is saturated or insoluble, then it can be precipitated out of the solution.

Uses of Bases

1. Magnesium hydroxide is a base that is used as an antacid to cure indigestion.
2. Dilute ammonium hydroxide solution is often used as a household cleansing agent.
3. Mild bases are used to rub over that area after the insect bite to neutralise the effect of the acids injected by the insects like ants.
4. Some amino acids are basic in nature like Arginine \({\rm{(Arg)}}\), Lysine \({\rm{(Lys)}}\), and Histidine; they are a part of proteins in our body.
5. Sodium carbonate \(\left( {{\rm{N}}{{\rm{a}}_2}{\rm{C}}{{\rm{O}}_3} \cdot 10{{\rm{H}}_2}{\rm{O}}} \right)\) is used as washing soda for cleaning clothes and is also used for hard water treatment to remove metal ions.
6. Sodium bicarbonate \(\left( {{\rm{NaHC}}{{\rm{O}}_3}} \right)\) is used as baking soda in making cakes.
7. Sodium benzoate is used as a pickling agent in many salads and foods.
8. Calcium hydroxide \(\left( {{\rm{Ca}}{{({\rm{OH}})}_2}} \right)\) is a base that is used in the synthesis of Ammonia gas.
9. Bases are mostly used as \({\rm{pH}}\) regulators for water treatment.

Industrial Preparation of Base

• Bases are prepared by the direct union of a metal with oxygen. When metals are heated in air or oxygen, they form the oxides of the metals. Followed by this, when these oxides are dissolved in water, they make the hydroxides of metals, i.e., base. For example:
  1. Formation of Sodium Hydroxide \(({\rm{NaOH}})\)
     \(4{\rm{Na}} + {{\rm{O}}_2} \to 2{\rm{N}}{{\rm{a}}_2}{\rm{O}}\)
     \({\rm{N}}{{\rm{a}}_2}{\rm{O}} + {{\rm{H}}_2}{\rm{O}} \to 2{\rm{NaOH}}\)
  2. Formation of Calcium Hydroxide \(\left( {{\rm{Ca}}{{({\rm{OH}})}_2}} \right)\):
     \(2{\rm{Ca}} + {{\rm{O}}_2} \to 2{\rm{CaO}}\)
     \({\rm{CaO}} + {{\rm{H}}_2}{\rm{O}} \to {\rm{Ca}}{({\rm{OH}})_2}\)
• Bases are also formed by the action of water or steam on some active metals as some active metals like sodium and potassium react even with cold water to form hydroxides along with the evolution of hydrogen gas.
  \(2{\rm{Na}} + 2{{\rm{H}}_2}{\rm{O}} \to 2{\rm{NaOH}} + {{\rm{H}}_2} \uparrow \)
• Magnesium reacts with steam to form Magnesium oxide along with the evolution of hydrogen gas.
  \({\rm{Mg}} + {{\rm{H}}_2}{\rm{O}} \to {\rm{MgO}} + {{\rm{H}}_2} \uparrow \)

Summary

Bases are chemical substances that are bitter in taste, soapy to touch and turns red litmus solution or litmus paper to blue. Compounds that release hydroxyl ions in an aqueous solution are known as bases, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, and many more. A base is a chemical substance that donates electrons, accepts protons, or releases hydroxide \(({\rm{O}}{{\rm{H}}^ – })\) ions in the aqueous solution. Bases are defined based on different theories like Arrhenius; according to the Arrhenius theory of base; it is a chemical species that produces a hydroxide ion \(({\rm{O}}{{\rm{H}}^ – })\) in its solution. The Bronsted-Lowry theory defines a base as a proton acceptor. Lewis base is a compound or ionic species which can donate a lone pair of electrons to an acceptor compound. According to their degree of dissociation in aqueous solution and reactivity, bases are classified into the strong base, weak base, superbase, neutral base, and solid base. Bases are very useful in the household as well as industrial purposes.

FAQs on Preparation of Bases

Q.1. What is a base in chemistry?
Ans: A base is a chemical substance that donates electrons, accepts protons, or releases hydroxide \(({\rm{O}}{{\rm{H}}^ – })\) ions in the aqueous solution. Examples of bases include alkali metal hydroxides like sodium hydroxide, potassium hydroxide, etc., alkaline earth metal hydroxides, calcium hydroxide, magnesium hydroxide, etc., and soap.

Q.2. How are bases prepared?
Ans: Bases are prepared by different methods, such as (i) Bases are prepared by the direct union of a metal with oxygen. When metals are heated in air or oxygen, they form the oxides of the metals. Followed by this, when these oxides are dissolved in water, they make the hydroxides of metals, i.e., base. (ii) Bases are also formed by the action of water or steam on some active metals as some active metals like sodium and potassium react even with cold water to form hydroxides along with the evolution of hydrogen gas. (iii) Magnesium reacts with steam to form Magnesium oxide along with the evolution of hydrogen gas.

Q.3. What is the formula for a base in chemistry?
Ans: In chemistry, bases are chemical substances that release hydroxide \(({\rm{O}}{{\rm{H}}^ – })\) ions in the aqueous solution. They are represented by a general formula, \(‘{\rm{MOH}}’\). Where, \({\rm{M}}\) is the alkaline or alkaline earth metal. For example, sodium hydroxide \(\left( {{\rm{NaOH}}} \right)\) and potassium hydroxide \(\left( {{\rm{KOH}}} \right)\), etc.

Q.4. What are the 5 types of bases?
Ans: \(5\) types of bases are: (i) Strong Base – A base that completely dissociates into its ions in water or is a compound that is capable of removing a proton \(\left( {{{\rm{H}}^{\rm{ + }}}} \right)\) from a very weak acid is known as a strong base. Some examples of strong bases include sodium hydroxide \(\left( {{\rm{NaOH}}} \right)\) and potassium hydroxide \(\left( {{\rm{KOH}}} \right)\), etc. (ii) Weak Base – A base that incompletely dissociates in water is known as a weak base. (iii) Superbase – A superbase deprotonates better than a strong base. Such bases have very weak conjugate acids and are formed by mixing an alkali metal with its conjugate acid. Some examples of superbase include sodium hydride \({\rm{(NaH)}}\), ortho-diethynylbenzene dianion \({\left( {{{\rm{C}}_6}{{\rm{H}}_4}{{\left( {{{\rm{C}}_2}} \right)}_2}} \right)^{2 – }}\).  (iv) Neutral Base – A base that forms a bond with a neutral acid in such a manner that the acid and base share an electron pair from the base is known as a neutral base. (v) Solid Base – A solid base is active in solid-state. Such as silicon dioxide \({\rm{(Si}}{{\rm{O}}_{\rm{2}}}{\rm{)}}\) and \({\rm{NaOH}}\) mounted on alumina is a solid base.

Q.5. What is the weakest base in chemistry?
Ans: Ammonia \(\left( {{\rm{N}}{{\rm{H}}_3}} \right)\) is the weakest base in chemistry. It does not contain hydroxide ions, but it reacts with water to form ammonium ions and hydroxide ions.

Q.6. What are \(5\) uses of bases?
Ans: The \(5\) uses of bases are: (i) Magnesium hydroxide is a base that is used as an antacid to cure indigestion. (ii) Dilute ammonium hydroxide solution is often used as a household cleansing agent. (iii) Mild bases are used to rub over that area after the insect bite to neutralise the effect of the acids injected by the insects like ants. (iv) Some amino acids are basic in nature, like Arginine \({\rm{(Arg)}}\), Lysine \({\rm{(Lys)}}\), and Histidine, they are a part of proteins in our body. (v) Sodium carbonate \(\left( {{\rm{N}}{{\rm{a}}_2}{\rm{C}}{{\rm{O}}_3} \cdot 10{{\rm{H}}_2}{\rm{O}}} \right)\) is used as washing soda for cleaning clothes and is also used for hard water treatment to remove metal ions.

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