Page 246 - ICSE Chemistry 8

19. Iron(II) sulphate forms green crystals. How are these crystals formed? What happens when the
crystal is heated?

20. What happens when water in the form of steam is passed over red hot coke? Represent the reac on
with the help of a chemical equa on.

21. It is a crystalline form of carbon which is the hardest natural substance known. Name the substance
and discuss the structure of the substance with the help of a diagram. On what factors does the
value of this substance depend upon?
22. It is a type of charcoal which is black, porous and bri le solid. Name it and discuss how it is obtained.
Also write its physical proper es and uses.
23. Name the variety of coal which consists of 80–85% carbon content. What happens when it burns?

24. A gas M when enters the human blood stream combines with haemoglobin present in the blood
to form a compound called N. Name the gas and the compound formed. What happens when this
compound is formed?
25. Give reasons for the following statements.

(a) It is dangerous to sleep in a closed room with a coal fi re burning.
(b) One should not sleep near lime kilns.
(c) The automobile exhaust gases contain carbon monoxide.

232