Note on Bases

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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.

  • 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.
.

Very Short Questions

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.

0%
  • Bases which are soluble in water are called ______.

    All the answers are correct


    alkalene


    alkalyene


    alkalis


  • Bases turn methyl orange yellow and ______ pink.

    universal indicator


    blue litmus paper


    phenolphthalein


    blue litmus paper


  • Base turns red litmus paper into ______.

    reamins neutral


    yellow


    blue


    pink


  • ______produce hydroxyl ions (OH) in aqueous solution.

    both acid and base


    Acid


    Base


    Salt


  • What do you mean by a base?

    compound that gives proton in aqueous solution


    compound that gives positive ion in aqueous solution


    compound that is created by combination of a proton and a negative ion


    compound that gives negative ion in aqueous solution


  • Which one of the given choices is a base?

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  • What happens when NaOH is mixed with water?

    It disassociates into Na+ and OH-
    It disassociates into NaO- and H+
    Nothing happens
    Change in color is seen
  • Which is a soluble base in water?

    Fe(OH)3


    NaOH


    Zn(OH)2


    Cu(OH)2


  • Which one of the following is a weak base?

    Ca(OH)2
    NH4OH
    KOH
    NaOH
  • Washing soda is a ______.

    indicator


    salt


    base


    acid


  • The nature of toothpaste use at home is ______.

    non of the above
    acidic
    basic
    neutral
  • What is the pH range of a basic solution:

    greater then 7
    1 to 6
    7 to 7 only
    2 to 6
  • Organic base means:

    The bases that are made in laboratories
    The bases that are derived from living organisms
    The bases that are derived from minerals
    All of the above
  • Inorganic base means:

    The bases that are derived from minerals
    The bases that are found in sea.
    The bases that are derived from living organisms
    The bases that are made in laboratories
  • What do you mean by a salt?

    The bases that are found in sea.
    compound that gives negative ion in aqueous solution
    compound that gives proton in aqueous solution
    compound that is created by combination of a proton and a negative ion
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DISCUSSIONS ABOUT THIS NOTE

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mesepticeye

why does aqueous solution of acids contain replaceable hydrogen ions


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All alkali are bases but all bases are not alkali


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uses oe bases

uses of bases


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