Viva Questions With Answers On Basic Laboratory Techniques
Chemistry Lab ManualNCERT Solutions Class 11 Chemistry Sample Papers
1. Why is a Bunsen burner provided with air holes ?
Ans. To regulate the supply of air.
2. What type of flame would you use for general heating purpose ?
Ans. A non-luminous oxidising flame is used for general heating as it gives maximum heat due to complete combustion of hydrocarbons.
3. What is the use of a fume cup-board ?
Ans. It is used to perform those experiments which involve the production of poisonous gases or vapours.
4. Why is a broad flame used for bending a glass tube ? ’
Ans. If a narrow flame is used, folds are formed at the bend.
5. Why does glass not possess a sharp melting point ?
Ans. Glass is an amorphouse solid. It does not have a regular arrangement of constituent particles. Hence, it does not have a sharp melting point.
6. Which type of glass softens readily, soda lime glass or borosilicate glass ?
Ans. Soda lime glass.
7. Why is it required to round off the freshly cut edges of glass tube ?
Ans. Freshly cut edges of glass tube are sharp. They might injure fingers while handling.
8. Why should the tube be rotated while heating ?
Ans. The tube is rotated while heating in order to ensure uniform heating from all sides.
9. Why is the red hot tube bent slowly ?
Ans. Red hot tube is very soft. It might flatten if it is bent suddenly. Slow process of bending prevents flattening of glass tube.
10. What is the role of glycerine in the process of boring ?
Ans. Glycerine is used to lubricate the borer. This gives a smooth hole on boring.
11. Why should the diameter of the borer be less than the diameter of the tube to be inserted in the hole ?
Ans. This is done to ensure that the tube fits tightly in the hole.
12. What type of glass is preferred for drawing out a jet ?
Ans. Soda lime glass (soft glass) is used for drawing out a jet because it has lower melting point and hence softens easily.
13. Why is the glass tube of smaller diameter choosen for drawing out a jet ?
Ans. In order to draw a jet from tube of larger diameter the tube will have to be stretched too far which is not convenient.
14. What is the use of wash bottle ?
Ans. It is used for getting a thin stream of water required for washing or transferring a precipitate.