A-LevelChemistryAtoms, molecules and stoichiometry9701/12 · May/June 2011 · Q101 Mark
Tanzanite is used as a gemstone for jewellery. It is a hydrated calcium aluminium silicate mineral with a chemical formula Ca2AlxSiyO12(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?
Ax: 1, y: 1
Bx: 2, y: 3
Cx: 3, y: 3
Dx: 6, y: 1
✓ Correct answer
C: x: 3, y: 3
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