Question

White phosphorus has the molecular formula p4 and sulfur has the molecular formula s8. how many grams of white phosphorus contain the same number of molecules as 6.41 g of sulfur?

Answer 1

To solve this problem, we must first convert sulfur the mass of sulfur into number of moles. We know that molar masses of the elements are:

S = 32 g / mol

P = 31 g / mol

Therefore the molecular forms has molar masses of:

S8 = 8 (32 g / mol) = 256 g / mol

P4 = 4 (31 g / mol) = 124 g / mol

Therefore converting mass to moles for S8:

moles S8 = 6.41 g / (256 g / mol) = 0.025 mol S8

This amount should be equal to P4, hence the number of moles of P4 should also be:

moles P4 = 0.025 mol P4

Converting to mass:

mass P4 = 0.025 mol (124 g / mol)

mass P4 = 3.1 g