Verified answer

first calculate no. of moles of O2 ....

no. of moles of O2 = 5/32 = 0.1563 (molecular mass of O2 = 32 g/mole)

as S is in excess ....so amount of products will depend on amout of O2

now 3 moles of O2 gives 2 moles of SO3

so 1 mole of O2 will give 2/3 moles of SO3

so 0.1563 mole of O2 will give 2/3 X 0.1563 = 0.1042 moles of SO3

molecular mass of SO3 = 80 g /mole

so yield of SO3 in grams = 80 X 0.1042 = 8.336 g