Question

Phosporus has the molecular formula of P4 and the Sulfur has a molecular formula of S8. How many grams of P4 contains the same number of molecules as 12.87 g of S8 .

Thank ypu. Please Explain the steps.

Answer 1

Molar mass of S8 = 256.5200 g/mol;

weight of S8 = 12.87 grams;

Number of moles of S8 = weight / molar mass

= 12.87 / 256.5200

= 0.05012 moles.

Molar mass of P4 = 123.8950 grams/mol

Generally 1 mole = avagadro number of molecules.It is in same way for all the molecules. Instead of going for big avagado number we can handle this with just mole number.

So the question simply becomes homany grams of P4 will have same moles as 12.87 grams of P4 do.

Now we take the number of moles for P4 too as 0.05012 moles.

in general number of moles = weight / molar mass;

but we have number of moles and we need weight.

Weight = moles x molar mass

= 0.05012 moles x 123.8950 grams/mol

= 6.2096 grams of P4 will have same number of molecules as 12.87 grams of S8 do.