Step-by-step explanation:
To determine the number of molecules in 280.4 g of SO3, we need to use the following steps:
Calculate the molar mass of SO3:
S = 32.06 g/mol
O = 3 x 16.00 g/mol = 48.00 g/mol
Molar mass of SO3 = 32.06 + 48.00 = 80.06 g/mol
Use the molar mass to convert grams to moles:
280.4 g SO3 x (1 mol SO3/80.06 g SO3) = 3.502 mol SO3
Use Avogadro's number (6.022 x 10^23 molecules/mol) to convert moles to molecules:
3.502 mol SO3 x (6.022 x 10^23 molecules/mol) = 2.106 x 10^24 molecules of SO3
Therefore, there are approximately 2.106 x 10^24 molecules of SO3 in a 280.4 g sample of SO3.