Acids, Bases and Salts Chemistry
Chemistry
Acids, Bases and Salts
07
Acids, bases and salts are used for various activities in our day to day life. To
inquire into your prior knowledge about acids, bases and salts, do the following
assignment.
Assignment - 7.1
Given below are several substances which we frequently use in our day to day
life. Classify them as acids, bases and salts and tabulate.
Lime juice, Jeewani solution, antacid tablets, milk of magnesia, toothpaste,
vinegar, salt, lime, soap, vitamin C tablets, saline solution
7.1 Acids
When you were answering the assignment 7.1 above, you could have classified
lime juice, vinegar and vitamin C in that list under the acids.
You have used various acids in the laboratory experiments also. Hydrochloric acid
(HCl), nitric acid (HNO3) and sulphuric acid (H2SO4) are some acids that are often
used in the laboratory.
Figure 7.1 - Some acids that are being frequently used
When considering the formulae of the above acids it is clear that hydrogen (H) is a
component element in all those acids.
²² What is an acid@
An acid is a compound that releases hydrogen ions (H+) in an aqueous medium.
Hydrochloric acid ionises as follows in the aqueous medium and releases H+ ions.
For free distribution 190
, Acids, Bases and Salts Chemistry
HCl (aq) H+ (aq) + Cl- (aq)
Based on the strength of releasing H+ ions in the aqueous medium, acids are
classified as strong acids and weak acids.
²² Strong acids
The acids that release H+ ions by complete ionisation in aqueous medium are strong
acids. It means that all such acid molecules are dissociated into H+ ions and the
corresponding negative ions in water. For example, in a solution of hydrochloric
acid which is a strong acid, there are only H+ ions and Cl- ions but no free HCl
molecules.
Given below are a few examples for some strong acids and how they ionise in the
aqueous medium.
• Hydrochloric acid (HCl)
HCl (aq) H+ (aq) + Cl- (aq)
• Sulphuric acid (H2SO4) 191
H2SO4 (aq) 2H (aq) + SO4 (aq)
+ 2-
• Nitric acid (HNO3)
HNO3 (aq) H+ (aq) + NO3 -(aq)
²² Weak acids
The acids which release H+ ions in aqueous medium by incomplete or partial
ionisation are called weak acids. This means that in aqueous medium, only a fraction
of such acid molecules are dissociated into H+ ions and relevant negative ions. The
unionised molecules remain as molecules themselves in aqueous solution.
Examples for weak acids:
Acetic acid (CH3COOH)
Carbonic acid (H2CO3)
Phosphoric acid (H3PO4)
Most of the acids in laboratory stores are concentrated acids. Dilute acids of
required concentration can be prepared by mixing such concentrated acids with
water. Acids of low concentration are known as dilute acids.
191 For Free Distribution
Chemistry
Acids, Bases and Salts
07
Acids, bases and salts are used for various activities in our day to day life. To
inquire into your prior knowledge about acids, bases and salts, do the following
assignment.
Assignment - 7.1
Given below are several substances which we frequently use in our day to day
life. Classify them as acids, bases and salts and tabulate.
Lime juice, Jeewani solution, antacid tablets, milk of magnesia, toothpaste,
vinegar, salt, lime, soap, vitamin C tablets, saline solution
7.1 Acids
When you were answering the assignment 7.1 above, you could have classified
lime juice, vinegar and vitamin C in that list under the acids.
You have used various acids in the laboratory experiments also. Hydrochloric acid
(HCl), nitric acid (HNO3) and sulphuric acid (H2SO4) are some acids that are often
used in the laboratory.
Figure 7.1 - Some acids that are being frequently used
When considering the formulae of the above acids it is clear that hydrogen (H) is a
component element in all those acids.
²² What is an acid@
An acid is a compound that releases hydrogen ions (H+) in an aqueous medium.
Hydrochloric acid ionises as follows in the aqueous medium and releases H+ ions.
For free distribution 190
, Acids, Bases and Salts Chemistry
HCl (aq) H+ (aq) + Cl- (aq)
Based on the strength of releasing H+ ions in the aqueous medium, acids are
classified as strong acids and weak acids.
²² Strong acids
The acids that release H+ ions by complete ionisation in aqueous medium are strong
acids. It means that all such acid molecules are dissociated into H+ ions and the
corresponding negative ions in water. For example, in a solution of hydrochloric
acid which is a strong acid, there are only H+ ions and Cl- ions but no free HCl
molecules.
Given below are a few examples for some strong acids and how they ionise in the
aqueous medium.
• Hydrochloric acid (HCl)
HCl (aq) H+ (aq) + Cl- (aq)
• Sulphuric acid (H2SO4) 191
H2SO4 (aq) 2H (aq) + SO4 (aq)
+ 2-
• Nitric acid (HNO3)
HNO3 (aq) H+ (aq) + NO3 -(aq)
²² Weak acids
The acids which release H+ ions in aqueous medium by incomplete or partial
ionisation are called weak acids. This means that in aqueous medium, only a fraction
of such acid molecules are dissociated into H+ ions and relevant negative ions. The
unionised molecules remain as molecules themselves in aqueous solution.
Examples for weak acids:
Acetic acid (CH3COOH)
Carbonic acid (H2CO3)
Phosphoric acid (H3PO4)
Most of the acids in laboratory stores are concentrated acids. Dilute acids of
required concentration can be prepared by mixing such concentrated acids with
water. Acids of low concentration are known as dilute acids.
191 For Free Distribution
