ChemIONS

Let's start with the ideal gas equation. PV=nRT STP means 1 atm of pressure and 25ºC or 298.15 ºK. So, just replace the values (1 atm)(0.3 L) = n (0.082 atm·L/ mole· ºK)(298.15 ºK) that way you can get the number of moles. n = 12.27 x 10^-3 moles you also know n = weight / molecular weight and you just replace the 6g value =P mw = 6g / 12.27 x 10^-3 moles mw = 489 g/mol hope this works, good luck