Question

The cheap compound having high melting point used in furnace is
A. Lead oxide
B. Calcium oxide
C. Mercury oxide
D. Zinc oxide

Answer 1

Hint: The compound which has a very high melting point does not melt at the high temperature of the furnace. Calcium oxide has a high melting point due to the strong bond between calcium and oxygen.

Complete Step by Step Answer:
Furnace works at a very high temperature. Thus the metal oxide should have a very high melting point to work at that temperature otherwise the metal oxide will burn. In calcium oxide calcium is an electropositive and oxygen is an electronegative element. So, they form a very strong bond between them and possess a very high melting point. Thus it is used in the furnace.
Thus the correct option is B.

Additional information: Calcium carbonate undergoes thermal decomposition in presence of heat to form calcium oxide along with carbon dioxide gas.
The reaction can be given as follows:
$CaC{{O}_{3}}\to CaO+C{{O}_{2}}$. In this reaction one mole of calcium carbonate is heated to form one mole of metal oxide ore that is calcium oxide along with carbon dioxide gas. On heating limestone or calcium carbonate decomposes to calcium oxide and carbon dioxide gas. In this reaction heat is needed, so it is an endothermic reaction.

Note: Calcium oxide is an oxide of calcium, an alkaline earth metal. Calcium oxide has high basic properties. It is a basic gas. On treatment with water it forms calcium hydroxide which is highly basic hydroxide.