Question

The chemical formula of feldspar is:
A. $KAlS{i_2}{O_8}$
B. $N{a_3}Al{F_6}$
C. $NaAl{O_8}$
D. ${K_2}{O_4}A{l_2}{(S{O_4})_4}Al{(OH)_4}$

Answer 1

Feldspar is a group of rock-forming tectosilicate minerals. These minerals are about $41\%$ of earth’s crust by weight. We know that there are different types of rocks among them the feldspar is found in igneous rock and also present in metamorphic rock. Feldspar is made up of elements like potassium, aluminum, sulphate, hydroxides. Choose one formula from above and tick it correct.

Complete step-by-step answer: Feldspar is a compound which means field flake, so as we know that the rocks by which earth crust is formed are igneous, metamorphic and sedimentary so this compound is found in both igneous and metamorphic rocks. But mostly it forms minerals and constitutes roughly two third of igneous rocks. It consists of tectosilicates, silicate minerals in which silicon ions are linked or we can say shared by oxygen ions. As we know about crystal three dimensional structure they also have a three dimensional structure in which they form a tetrahedron like geometry and are linked together.
The compound consists of elements like it is made up of potassium which is cation there and aluminum also, anions are of two types present in the formula these are sulfur and oxides. So, the formula should be option A which is $KAlS{i_2}{O_8}$ .

Option A is correct.

Note: There are alkali feldspar which are further grouped up containing sodium, potassium. They are known by the names orthoclase, sanidine, microcline and anorthoclase. You read them in your higher classes. When the alkali metal gets changed from potassium, sodium to barium some other names of feldspar are seen like celsian.