How Do You Calculate the Molar Mass of an Unknown Gas?

[chem]

HELP PLEASE! Molar mass of unknown gas

Hey, I would really appreciate a little help. I'm kind of confused :( with this question:

A sample bulb contained 0.712 g of H2 (g) at a certain temperature and pressure. Under the same conditions of temperature an pressure, the bulb can hold 13 g of an unknown gas. What is the molar mass of the unknown mass?? Does anybody know if I have to apply the ideal gal law and how??

Thank you!

 

[siddharth]

Yeah. Write down the Ideal gas law in both the cases. Do you see how to solve it now?

 

[chem]

given the only data in the problem, do i have to assume STP in both?

Thanks!

 

[arunbg]

No, the result is independent of the temperature, pressure and volume, if we assume ideal gas behaviour.
Just write the ideal gas equations and solve.