First, you need grams but you have moles. Find out the total molar mass of SiO₂ Si = 28.085 g/mol Si O₂ = 32 g/mol O₂ Add them together to get the molar mass 28.085 g/mol Si + 32 g/mol O₂ = 60.085 g/mol SiO₂ Multiply the molar mass of SiO₂ by the number of moles you have of the same substance: 60.085 g/mol SiO₂ × 0.125 mol SiO₂ = 7.51 grams SiO₂
