3. Study of Acids, Bases and Salts
(i) Simple definitions in terms of the molecules and their characteristic properties.
(ii) Ions present in mineral acids, alkalis and salts and their solutions; use of common acid-base indicator (litmus, methyl orange and phenolphthalein) and pH paper to test for acidity and alkalinity.
- Examples with equation for the ionisation/dissociation of ions of acids, bases and salts.
- Acids form hydronium ions (only positive ions) which turn blue litmus red, alkalis form hydroxyl ions (only negative ions) with water which turns red litmus blue.
- Salts are formed by partial or complete replacement of the hydrogen ion of an acid by a metal. (To be explained with suitable examples).
- Introduction to pH scale to test for acidity, neutrality and alkalinity by using pH paper or Universal indicator.
(iii) Definition of salt; types of salts. Types of salts: normal salts, acid salt, basic salt, complex salts (definition and examples).
(iv) Action of dilute acids on salts. Decomposition of hydrogen carbonates, carbonates, hydrogen sulphites, sulphites and sulphides by appropriate acids with heating if necessary. (Relevant laboratory work must be done).
(v) Methods of preparation of Normal salts with relevant equations. (Details of apparatus or procedures not required). Methods included are: Direct combination; Displacement; Precipitation (double decomposition); Neutralization of insoluble base; Neutralisation of an alkali (titration); Action of dilute acids on carbonates and bi-carbonates.