In 1985 benitoite became the California "state gemstone." Found only in a tiny mine near Coalinga, California, it is a silicate of barium and titanium with trace impurities that cause a range of hues from colorless to blue to pink. Its general formula is BaTi (SiO3) 3. If a 15-carat stone were pure BaTi (SiO3) 3, how many moles of oxygen would it contain? (There are exactly 5 carats per gram.)

Question

Madison Leblanc

Chemistry

3 April, 11:01

In 1985 benitoite became the California "state gemstone." Found only in a tiny mine near Coalinga, California, it is a silicate of barium and titanium with trace impurities that cause a range of hues from colorless to blue to pink. Its general formula is BaTi (SiO3) 3. If a 15-carat stone were pure BaTi (SiO3) 3, how many moles of oxygen would it contain? (There are exactly 5 carats per gram.)

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Tucker Mccarty · Answer 1

Answer is: there are 0,06525 moles of oxygen in 15 carat benitoite.

m (BaTi (SiO₃) ₃) = 15 carat : 5 carat/g = 3 g.

M (BaTi (SiO₃) ₃) = Ar (Ba) + Ar (Ti) + 3Ar (Si) + 9Ar (O) · g/mol.

M (BaTi (SiO₃) ₃) = 137,33 + 47,87 + 3 · 28,09 + 9 · 16 · g/mol.

M (BaTi (SiO₃) ₃) = 413,5 g/mol.

n (BaTi (SiO₃) ₃) = m (BaTi (SiO₃) ₃) : M (BaTi (SiO₃) ₃).

n (BaTi (SiO₃) ₃) = 3 g : 413,5 g/mol.

n (BaTi (SiO₃) ₃) = 0,00725 mol.

In one molecule of benitoite there are nine oxygen atoms.

n (O) = 9 · 0,00725 mol.

n (O) = 0,06525 mol.