Question

Different forms of silica such as quartz, tridymite and cristobalite are as follows:
Quartz $\stackrel{{870}^{\circ }C}{⟶}$ Tridymite $\stackrel{{1470}^{\circ }C}{\rightleftharpoons }$ Cristobalite

$\left(Si{O}_2\right)$ $\left(Si{O}_2\right)$ $\left(Si{O}_2\right)$

The structure possessed in them is:

• A. Sheet silicate
• B. Three-dimensional silicate
• C. Chain silicate
• D. Cyclic or ring silicate

Answer 1

The correct option is B

Three-dimensional silicate

Three-dimensional sheet silicates or framework minerals: Complete sharing of all four oxygen atoms in all tetrahedral gives a three-dimensional network. The empirical formula for such a substance would be $(Si{O}_2{)}_n$, i.e. we would have silica. This type of structure is characteristic of three forms of silica, i.e. quarts, tridymite and crystallobalite.