Question

The silicate anion in the mineral kaolinite is a chain of three $Si{O}_4$ tetrahedral that share corners with adjacent tetrahedral. The mineral also contains ${Ca}^{2+}$ ions, ${Ca}^{2+}$ ions, and water molecules in a 1 :1 :1 ratio. Mineral is represented as :

• A. $CaCuS{i}_3{O}_{10}.H_{2}O$
• B. $CaCuS{i}_3{O}_{10}.2H_{2}O$
• C. ${Ca}_2{Cu}_2{Si}_3{O}_{10}.2H_{2}O$
• D. None of these

Answer 1

Answer: (C)

${Ca}_2{Cu}_2{Si}_3{O}_{10}.2H_{2}O$

The formula of silicate with three $Si{O}_4$ tetrahedral that share corners with adjacent tetrahedral = $S{i}_3{O}_1{0}^{8-}$

Charge on $Ca=+2$

Charge on $Cu=+2$

Charge on $H_{2}O=0$

To balance the $-8$ charge of silicate with $C{a}^{2+},C{u}^{2+}$ and $H_{2}O$ in ration $1:1:1$ number of each required $=2$

Hence the formula of mineral$=C{a}_{2}C{u}_{2}S{i}_3{O}_{10}.2H_{2}O$