Q.Solid A is a very hard electrical insulator in solid as well as in molten state and melts at extremely high temperature. What type of solid is it?

A solid that is very hard, an electrical insulator in both solid and molten states (no free ions or electrons) and melts at an extremely high temperature is held together by a continuous thre …

Step 1 – Read the clues.

• Very hard $\Rightarrow$ strong directional bonding throughout.
• Insulator in solid and molten state $\Rightarrow$ no mobile charge carriers (rules out ionic solids, which conduct when molten, and metals, which conduct always).
• Extremely high melting point $\Rightarrow$ a giant network of strong bonds must be broken.

Step 2 – Match to a solid type. …

Eliminate by conductivity: molten insulation rules out ionic and metallic solids; combined with extreme hardness and very h …

• Answering 'ionic solid'; ionic solids conduct in the molten state, so the molten-insulator clue rules them out. …