Question

Tanzanite is used as a gemstone for jewellery. It is a hydrated calcium aluminium silicate mineral
with a chemical formula Ca2Al xSiyO12(OH).6½H2O. Tanzanite has Mr of 571.5.

Its chemical composition is 14.04 % calcium, 14.17 % aluminium, 14.75 % silicon, 54.59 % oxygen
and 2.45 % hydrogen.

(Ar values: H = 1.0, O = 16.0, Al = 27.0, Si = 28.1, Ca = 40.1)

What are the values of x and y?

x y
A 1 1
B 2 3
C 3 3
D 6 1