How many molecules of sulfur dioxide are present in 72 g of the substance?

To determine the number of molecules of sulfur dioxide in 72 g of the substance, we first need to calculate the number of moles of sulfur dioxide present. The molar mass of sulfur dioxide (SO2) is approximately 64 g/mol. Therefore, 72 g of sulfur dioxide is equal to 72 g / 64 g/mol = 1.125 moles. Next, we use Avogadro's number, which is 6.022 x 10^23 molecules/mol, to convert moles to molecules. Therefore, there are approximately 6.78 x 10^23 molecules of sulfur dioxide in 72 g of the substance.