Chemistry help please .....?

Question

At 500 degree celsius and 699 Torr pressure, the mass density is 3.71gdm^-3. Calculate the molecular formula of sulphur under these conditions.

Ive been trying to answer this question for ages and i cant figure out how to do it. Any help will be much appreciated.

Thank you

Answer 1

PV = nRT where n = m/MM

MM = (mRT)/PV where m = 3.71 g R = 0.08206...Latm/molK T = 773 K P = 699/760 atm V = 1 L

This will get you a MM, Molar Mass. Dividing this value by the molecular weight of S (32.06 g/mol) will give you the molecular formula.

Answer 2

You know the number of grams in 1 L (it is 3.71).

You can work out the number of moles using

PV = nRT

(Make sure your units match; for example, if R is in L atm mol-1 K-1, then use P = 699/760 atm; V = 1 L because we have chosen 1 L - same thing as 1 dm3 - and of course you want T in Kelvin).

Then simply divide the number of grams by the number of moles, and that will give you the molar mass.

The atomic mass of S is 32. So if the molecular formula is S subscript m, the molar mass will be 32 x m.

Answer 3

say what now ???