Important questions based on NCERT syllabus for Chapter 2 - Acids, Bases and Salts:
Question-1: Write a short note on pH.
Solution: 1. The pH is the measure of how acidic or basic is an aqueous solution.
2. It is measured in terms of hydrogen ion concentraion in the solution. Thus pH or power of hydrogen.
3. The pH values range from 0 to 14. Values less than 7 represent an acidic solution, above 7 indicate a basic solution and 7 is neutral
Question-2: Name three compounds of calcium which are used in day-to-day life and write one important use of each of them.
Solution: The three compounds of calcium and their uses are :
- Slaked lime [Calcium hydroxide, Ca(OH)2] – used for the manufacture of bleaching power.
- Bleaching powder [Calcium oxychloride, CaOCl2] – used as bleaching agent in laundry.
- Plaster of Paris [Calcium sulphate hemihydrate, Ca(SO)4 (1/2) H2O ] – used to plaster the fractured bones.
Question-3: Why should curd and sour substances not be kept in brass and copper vessels?Why should water be never added dropwise to concentrated sulphuric acid?
Solution: 1. Curd and sour substances contain acids.
2. They would react with the surface of metal vessels such as that of brass and copper to produce harmful substances.
3. While diluting an acid, water should not be added dropwise to a concentrated acid because the heat generated may cause the mixture to splash out.