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Bases

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Overview

A base is defined as any substance which releases hydroxyl ions (OH-) when dissolved in water. Bases which are soluble in water are called alkalies. This note about bases provides information about bases its properties and common uses.
Bases

A base is defined as any substance which releases hydroxyl ions (OH-) when dissolved in water. Sodium hydroxide and ammonia are bases because they give hydroxyl ions in water.

NaOH → Na+ + OH-

Sodium hydroxide

NH3 + H2O → NH4+ + OH-

Ammonia (Ammonium ion)

Bases which are soluble in water are called alkalies. Some bases are not soluble in water. They are not alkalies. Thus, all alkalies are bases but all bases are not alkalies. Sodium oxide is called soda and potassium hydroxide is called caustic potash.

Some are given below:

S.N Bases Formula
1. Sodium hydroxide NaOH
2. Potassium hydroxide KOH
3. Aluminum hydroxide Al(OH)3
4. Ammonium hydroxide NH4OH
5. Sodium oxide Na2O
6. Potassium oxide K2O
7. Magnesium oxide MgO

Properties of bases

Physical properties:

  1. They are soapy in touch.
  2. They have a bitter test.
  3. They turn red litmus paper into blue.
  4. They turn turmeric paper brown.
  5. They turn methyl orange yellow and phenolphthalein pink.

Chemical properties:

  1. They produce hydroxyl ions (OH-) in aqueous solution.
  2. They neutralize acids to form salt and water.
    KOH + HCl → KCl + H2O
    Potassium hydroxide + Hydrochloric acid → Potassium chloride + Water
  3. Bases react with carbon dioxide to form carbonate
    K2O + CO2 → K2CO3
  4. They react with metals of the type zinc and aluminum and produce hydrogen.
    Zn + 2NaOH → NaZnO2 + H2
  5. When a base is heated with an ammonium salt, ammonia gas is given off. It can recognized by its extremely pungent smell.
    NaOH + NH4Cl → NaCl + H2O + NH3
    Sodium hydroxide + Ammonium chloride → Sodium chloride + Water + Ammonia

Some bases which are commonly used in daily life are:

S.N Bases Uses
1. Sodium hydroxide In the manufacture of soap.
2. Potassium hydroxide Firewood ash-filtered wood ash is used for washing clothes in rural areas.
3. Aluminum hydroxide As medicine (antacid) for gastric patients.

Differences between acids and bases:

S.N Acids Bases
1. Turn blue litmus into red. Turn red litmus into blue.
2. React with metals to give the salt and hydrogen gas. Normally do not react with metals. Only some metals like zinc, aluminum and tin react to give hydrogen.
3. Are corrosive to skin. Are slipper to touch.
4. Are sour in taste. Are bitter in taste.
5. React with bases to give salts and water. React with acids to give salt and water.
6. An aqueous solutions of acids contain replaceable hydrogen ions. An aqueous solution of the base contains replicable hydroxyl ions.
7. Give no color with phenolphthalein. Give red color with phenolphthalein.
Things to remember
  • A base is defined as any substance which releases hydroxyl ions (OH-) when dissolved in water. Sodium hydroxide and ammonia are bases because they give hydroxyl ions in water.
  • Bases which are soluble in water are called alkalies.
  • All alkalies are bases but all bases are not alkalies.
  • Physical properties of bases include its soapy touch, bitter taste etc.
  • It includes every relationship which established among the people.
  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.
Videos for Bases
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Bases
Questions and Answers

Metallic oxide and hydroxide are called base.
The chemical properties of base are as follows:

  • A base reacts with acid to form a salt of the acid and water.
    NaOH + HCL → NaCl + H2O
  • The base reacts with carbon dioxide to produce carbonate salt and water.
    2NaOH + CO2 → Na2CO3 + H2O

Salt:
Sodium Chloride - It is used in our balanced diet.
Sodium bicarbonate - It is used as a baking powder.
Base:
Potassium hydroxide – It is used as ash to wash utensils and clothes.
Sodium hydroxide – washing soda is used as manufacture of soap.

The differences between base and alkali are as follows:

Base 		Alkali
All metallic oxides are called base. Water soluble metallic oxides and hydroxides are called alkali.
They may or may not be soluble in water. They are soluble in water.
Examples: Ca0, K2O etc. Examples: NaOH, KOH etc.

All alkalis are bases but all bases are not alkalis because all bases are not soluble in water and water soluble bases are called alkalis.

  • Milk is a neutral substance.

Sour milk is acidic substance.

  • Bases are hard when touched.

Bases are soapy when touched.

  • Water added to alkali makes acid.

Water added to alkali make hydroxide ion.

  • The mixture of acid and phenolphthalein is pink in colour.

The mixture of base and phenolphthalein is pink in colour.

  • Our gastric glands of THE stomach produce sulphuric acid.

Our gastric glands of THE stomach produce hydrochloric acid.

  • All the salts are salty.

All salts are not salty. Some are bitter in taste.

The physical properties of base are:

  1. They are soapy in touch.
  2. They have a bitter test.
  3. They turn red litmus into blue.
  4. They turn turmeric paper brown.
  5. They turn methyl orange yellow and phenolphthalein pink.

The difference between acid and base are:

S.N Acids Bases
1. Turn blue litmus into a red. Turn red litmus into blue.
2. React with metals to give a salt and hydrogen gas. Normally do not react with metals. Only some metals like zinc, aluminum and tin react to give hydrogen.
3. Are corrosive to skin. Are slippery to touch.
4. Are sour in taste. Are bitter in taste.
5. React with bases to give salts and water. React with acids to give salt and water.
6. Aqueous solutions of acids contain replaceable hydrogen ions. Aqueous solution of a base contains replicable hydroxyl ions.
7. Give no color with phenolphthalein. Give red color with phenolphthalein.
Quiz

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