Question

The silicate anion in the mineral kinoite is a chain of three $Si{O_4}$ tetrahedral that shares corners with adjacent tetrahedral. The mineral also contains $C{a^{2 + }}$ ions, $C{u^{2 + }}$ ions and water molecules in a $1:1:1$ ratio. The mineral is represented by:
A.\[CaCuS{i_3}{O_{10}}{H_2}O\]
B.$C{a_2}C{u_2}S{i_3}{O_{10}}{H_2}O$
C.$C{a_2}C{u_2}S{i_3}{O_{10}}2{H_2}O$
D.None of the above

Answer 1

Hint: Silicate ions can be represented by making a silicate ion, then making 4 bonds with four oxygen atoms, all single bonds. The adjacent silicon atoms which continue the chain, bond with the next silicon atom and so on. While the other two atoms both have a single negative charge each.

Complete answer:
Silicate ions can be represented by making a silicate ion, then making 4 bonds with four oxygen atoms, all single bonds. The adjacent silicon atoms which continue the chain, bond with the next silicon atom and so on. While the other two atoms both have a single negative charge each.
Now the general formula for such a silicon chain would be, let’s say we have to make a chain of 3 silicon atoms, there would be two oxygen atoms between them and two oxygen atoms with a negative charge attached to each of them. The two-silicon atom not adjacent to each other also have two oxygen atoms with negative charge attached to them, so the general formula would be
$S{i_3}{O_{10}}^{8 - }$
Now it is given that calcium and copper and water are present, that too in the same proportion.
We have to make the negative charge on the silicon chain neutral, so we need two atoms of copper and calcium each, which add up to eight and also, they are in equal proportion.
Also, water is also in the same proportion, water is neutral so we can directly add it till it satisfies the ratio given
The formula becomes
$C{a_2}C{u_2}S{i_3}{O_{10}}2{H_2}O$
It satisfies the ratio given and also it has a chain of silicate ions.
Hence the correct answer is option C, $C{a_2}C{u_2}S{i_3}{O_{10}}2{H_2}O$

Note:
Zeolites and other silicate products can be produced by indulging double level silicates which are used for various purposes, one of them being absorbents, ion exchange and desiccants. Silicates are also used for making glass and ceramics.