Bases

What are the uses of Bases

by

What are the uses of Bases

Uses of Bases

1. Calcium Hydroxide (Slaked lime) [Ca(OH)2]

  • It is used to neutralize the acidity in soils.
  • It is an ingredient in whitewash and mortar.
  • It is a component of the Bordeaux mixture used for protecting agricultural crops from pests.
  • It is used in the preparation of dry mixes for painting and decorating.

2. Magnesium Hydroxide (Milk of magnesia) [Mg(OH)2]

  • It is used as an antacid or a laxative. It helps to correct excess acidity in the stomach.

3. Sodium Hydroxide (Caustic soda) (NaOH)

  • It is used in the manufacture of paper, textiles, and detergents.
  • In homes, it is occasionally used to unblock drains.
  • It is used in the manufacture of soaps and detergents.

Table lists some of the common bases and their uses.

BasesUses
Sodium hydroxide
  1. In the manuacture of   soaps, textile, paper, medicines
  2. In the refining of petroleum
Ammonium hydroxide
  1. As a reagent in the laboratory
  2. In making fertilizers, rayon, plastics and dyes
Calcium hydroxide
  1. In making cement and mortar
  2. In making bleaching powder
  3. In whitewashing
  4. In removing acidity of soils

 

BaseAmmoniaSodium hydroxideCalcium hydroxideMagnesium hydroxideAluminium oxide
UseTo make

  • nitric acid
  • fertilisers
  • nylon
  • cleaning agent

To prevent coagulation of latex

To make

  • soap
  • detergents
  • bleaching agents
To make

  • cement
  • bleaching powder

To neutralise acidity in soils

To make

  • toothpaste
  • antacids
To make antacids

People also ask

 

General Properties of Bases

by

General Properties of Bases

Some of the characteristic properties of bases are:

  • Bases are bitter to taste a bitter taste is characteristic of all bases.
  • Bases may or may not be soluble in water Bases that can dissolve in water are called alkalis. Some examples of soluble bases or alkalis are sodium hydroxide, potassium hydroxide, and calcium hydroxide.
    Like acids, bases can be strong or weak.
    Strong bases are very corrosive and can burn the skin.
    These bases should be handled carefully. Caustic soda or sodium hydroxide (NaOH) and caustic potash or potassium hydroxide (KOH) are strong and corrosive bases.
    On the other hand, copper hydroxide [Cu(OH)2], zinc hydroxide [Zn(OH)2], and ammonium hydroxide (NH4OH) are weak bases
  • The solutions of bases in water give a soapy touch. When dissolved in water they produce hydroxide ions (OH–) in solution.
    General Properties of Bases 1
  • They turn red litmus paper blue.
    Take some soap solution in a test tube. Dip the tip of a red litmus paper into it. You will see that red litmus paper turns blue. This indicates that the soap solution contains a base.
  • They react with acids to produce salt and water.
    NaOH + HCI  →  NaCl + H2O
    2KOH + H2SO4  →  CuSO4 + 2H2O
    Cu(OH)2 + H2SO4  →  CuSO4 + 2H2O
    In these reactions, the acid and the base neutralize each other. Therefore, these reactions are called neutralization reactions.
    Thus, a neutralization reaction may be defined as a reaction between an acid and a base, producing salt and water.
    This neutralization reaction may be explained as follows. You know, all acids provide H+ ions and all bases provide OH– ions in aqueous solution. Let us see what happens when HCl and NaOH react together.
    HCl + NaOH  →  NaCl + H2O
    or   H+ + Cl– + Na+ + OH– →  Na+ + Cl– + H2O
    or   H+ + OH– →  H2O
    Thus, during neutralization of an acid with a base or vice versa H+ ions (from acid) and OH– ions (from base) combine to produce H2O molecules.
  • The oxides which produce acids in aqueous solutions are called acidic oxides which are usually the oxides of nonmetals. Acidic oxides react with bases to give salts and water.
    General Properties of Bases 2
  • When a base is heated with an ammonium salt, ammonia gas, another salt and water are produced. For example, when sodium hydroxide is heated with ammonium chloride, the products formed are sodium chloride, water and ammonia gas.
    General Properties of Bases 3
    Ammonia gas is recognized by its pungent smell.
  • Bases react with certain salts to produce another salt and another base. For example, when NH4OH is added to a solution of Al2(SO4)3, (NH4)2SO4 and Al(OH)3 are produced.General Properties of Bases 4

Bases need water to show basic properties

  1. A base needs to dissolve in water to show basic properties. Bases in dry condition or dissolved in organic solvents do not exhibit basic properties.
  2. A base needs water to produce hydroxide ion which is responsible for basic properties.
  3. Ammonia is a base. It consists of ammonia molecules.
    General Properties of Bases 5
  4. Ammonia does not contain OH– ions. It needs water to help it to ionise to produce OH– ions.
  5. Experiment studies the need of water for ammonia to show its basic properties.

People also ask

Bases need water to show basic properties experiment

Aim: To investigate whether a base needs water to show its basic properties.
Problem statement: Does a base need water to show its basic properties?
Hypothesis: A base needs water to show its basic properties.
Variables:
(a) Manipulated variable : Types of solvents
(b) Responding variable : Change in colour of red litmus paper
(c) Controlled variable : Type of base
Operational definition: A red litmus paper is used to test if a solution is alkaline. Alkaline solutions turn red litmus paper blue.
Materials: Ammonium chloride, calcium hydroxide, calcium oxide, distilled water, trichloromethane and red litmus paper.
Apparatus: Test tubes, boiling tube, beakers, filter funnel, delivery tubes, Bunsen burner, U-tube, stopper, dropper and test tube rack.
Procedure:

General Properties of Bases 6

  1. A solution of ammonia in water and a solution of ammonia in trichloromethane are prepared using the apparatus set-up shown below.
  2. Two test tubes are labelled and placed in a test tube rack.
  3. About 1 cm3 of the solution of ammonia in water is placed in the first test tube (I).
  4. About 1 cm3 of the solution of ammonia in trichloromethane is placed in the second test tube (II).
  5. A piece of dry red litmus paper is dropped into each of the two test tubes.
  6. Any changes that occur are observed and recorded in a table.

Observations:
Discussion:

  1. Ammonia gas is liberated when a mixture of ammonium salt is heated with an alkali.
    General Properties of Bases 7
  2. Ammonia gas is a covalent compound composed of ammonia molecules.
  3. In water, the ammonia molecules react with water and ionise to produce ammonium ions and hydroxide ions.
    General Properties of Bases 8
  4. The presence of mobile ions makes the aqueous solution of ammonia able to conduct electricity.
  5. The hydroxide ion turns red litmus paper blue.
  6. A solution of ammonia in trichloromethane is composed of only ammonia molecules. There are no ions present because the ammonia molecules cannot ionise in organic solvents. Without hydroxide ions, the solution does not show basic properties.

Conclusion:
The aqueous solution of ammonia shows basic properties. The hypothesis can be accepted.

What is the definition of a base in chemistry

by

What is the definition of a base in chemistry?

Bases
Bases are substances that are soapy to touch and bitter in taste.
Substances containing a base are called basic substances. Sodium hydroxide (NaOH) and calcium hydroxide [Ca(OH)2] are examples of bases used in the laboratory. Corn starch, fresh egg white, etc., are other examples of bases.
Bases may have a strong irritating odour and should be used with caution as they can harm the skin and eyes.

the-definition-of-an-acid-in-chemistry
Some bases

A base is a substance, usually the oxide or the hydroxide of a metal, which can react with an acid to produce salt and water.

For example, sodium oxide (Na2O), calcium oxide (CaO), cupric oxide (CuO), iron oxides (FeO, Fe2O3 etc.), sodium hydroxide (NaOH) and calcium hydroxide (Ca(OH)2 are all bases.

Certain substances are also called bases, though they do not fit into the above definition. For example, ammonia (NH3). It forms salt with an acid without giving water. So, it should not be treated as a base. But ammonium hydroxide (NH4OH), the aqueous solution of NH3, is a base as it reacts with an acid to give salt and water

NH4OH + HCl  →  NH4Cl + H2O

Alkalis :
Bases that are soluble in water are called alkalis. For example, sodium hydroxide, potassium hydroxide, calcium hydroxide are soluble in water. Therefore, they are alkalis. But bases like copper hydroxide (Cu(OH)2 ferric hydroxide (Fe(OH)3), aluminium hydroxide (Al(OH)3 do not dissolve in water. They are, therefore, not alkalis.

Hence, all alkalis are bases, but all bases are not alkalis. Some of the bases are listed here in Table.

Oxides

Soluble hydroxidesInsoluble hydroxides

Sodium monoxide (Na2O)

Sodium hydroxide (NaOH)

Ferric hydroxide (Fe(OH)3).

Calcium oxide (CaO)

Potassium hydroxide (KOH)

Aluminium hydroxide

(Al(OH)3)

Cupric oxide (CuO)

ZnO

Calcium hydroxide (Ca(OH)2)

Ammonium hydroxide

NH4OH

Lime water, baking soda and washing soda are all bases.

People also ask

Preparation of Bases

by

Preparation of Bases

Bases can be prepared by the following methods.

1. By the direct union of a metal with oxygen Some metals when heated in air or oxygen form the oxides of the metals.
Preparation of Bases 1
These oxides when dissolves in water make the hydroxides of metals.

Na2O   +   H2O  →  2NaOH

K2O     +  H2O   →   2KOH

CaO     +  H2O   →   Ca(OH)2

2. By the action of water or steam on some active metals Some active metals like sodium and potassium react with cold water to form hydroxides with the evolution of hydrogen gas.

2Na + 2H2O  →  2NaOH + H2­

Magnesium reacts with steam to form magnesium oxide with the evolution of hydrogen gas.
Preparation of Bases 2
On passing superheated steam over red-hot iron, ferrosoferric oxide is formed and hydrogen gas is evolved.
Preparation of Bases 3
3. By heating carbonates of some metals When calcium carbonate is heated, calcium oxide and carbon dioxide are formed.

CaCO3   →  CaO + CO2­

Similarly, when zinc carbonate is heated, zinc oxide and carbon dioxide are formed

ZnCO3   →  ZnO + CO2­

4. By the action of an alkali on a salt solution For example, when an aqueous solution of sodium hydroxide is added to an aqueous solution of magnesium sulphate, magnesium hydroxide gets precipitated and sodium sulphate remains in the solution.
Preparation of Bases 4

People also ask