Silica covers an entire group of minerals, which have the general formula `SiO_2`, the most common of which is quartz, which is a framework silicate with `SiO_4` tetrahedra arranged in spirals. The spirals can turn in a clockwise or anticlockwise direction resulting in two mirror images, optically active, varieties of quartz.
The silicate anion in the mineral kinoite is a chain of three `SiO_4^(4-)` tetrahedra that share coners with adjacent tetrahedra. The mineral also contains `Ca^(2+)` ions, `Cu^(2+)` ions and water molecules in a 1 : 1 : 1 ratio. The mineral is represented as

Options

A. `CaCuSi_3 O_10. H_2O`
B. `CaCuSi_3O_10. 2 H_2O`
C. `Ca_2Cu_2Si_3O_10 .2 H_2O`
D. `CaCuSi_3O_10 . 3 H_2O`

Answer

C

Explanation

The mineral kinoite contains `Ca^(2+)` ions, `Cu^(2+)` ions and water molecules in a 1 : 1 : 1 ratio. So, the compound is `Ca_2Cu_2Si_3O_10 . 2H_2O`