A mineral consisted of 29.4% calcium, 23.5% sulfur and 47.1% oxygen. What is the empirical formula?

Step one calculate the moles of each element

that is moles = % composition/molar mass

molar mass of Ca = 40g/mol, S = 32 g/mol, O = 16 g/mol

moles of Ca = 29.4 / 40g/mol=0.735 moles, S = 23.5/32 = 0.734 moles, O = 47.1/16 = 2.94 moles

calculate the mole ratio by dividing each mole with smallest mole that is 0.734

Ca = 0.735/0.734 = 1, S = 0.734/0.734 = 1, O = 2.94 / 0.734 = 4

therefore the emipical formula = CaSO4