21.
The material used in the manufacture of lead pencil is

22.
Water can be separated from alcohol water mixture by

23.
In addition to hydrogen, the other abundant element present on Sun’s surface is

24.
The most abundant element by number in the living system is :

25.
What is the element required for solar energy conversion ?

26.
Major portion of the earth’s crust is mainly constituted by

27.
In surgery, metal pins are used for joining together broken bones. These metal pins remain uncorroded in the body. What is the material of these pins?

28.
Name two elements that find wide application in transistor industry.

29.
Which one is the naturally occuring heaviest element?

30.
Which of the following will replace hydrogen from acids to form salts ?