Final answer:
To find the number of moles in 695g of silicon dioxide, calculate its molar mass as the sum of the atomic masses of silicon and oxygen, then divide the given mass by the molar mass. The result is approximately 11.6 moles.
Step-by-step explanation:
To calculate the number of moles in 695g of silicon dioxide (SiO₂), we must first determine the molar mass of SiO₂. Silicon (Si) has an atomic mass of approximately 28.0855 grams per mole, and oxygen (O) has an atomic mass of approximately 16.00 grams per mole. Since SiO₂ has one silicon atom and two oxygen atoms, we can calculate its molar mass as:
Molar mass of SiO₂ = (1 × 28.0855) + (2 × 16.00) = 28.0855 + 32.00 = 60.0855 grams per mole.
Now, using the molar mass and the given mass of SiO₂, we can calculate the number of moles:
Number of moles = mass (g) / molar mass (g/mol)
Number of moles of SiO₂ = 695 g / 60.0855 g/mol
Number of moles of SiO₂ = 11.56 moles
Our final answer is expressed to three significant figures. Therefore, there are 11.6 moles of silicon dioxide in 695 grams of SiO₂.