chemistry gas law question!!!?

Question

I need an answer right away so please answer in full detail because i really don't understand this.

What is the molar mass of an ideal gas if a 0.622 g sample of this gas occupiies a volume of 300 mL at 35C and 789 mm Hg?

Ok, so i know i have to make the Celsius to Kelvin, but am i plugging this inter the PV=nRT equation? and what am i looking for?

Answer 1

n is the number of moles in the gas. But you have to make sure you use the right gas constant R for moles. R = 8.31 joule/(mole ºK). See http://en.wikipedia.org/wiki/Gas_law

In addition to converting ºC to ºK, you have to convert mm Hg to pascals, and volume to cubic meters.

1 Pa = 7.5*10^-3 mmHg

1 m^3 = 10^6 mL

Use the gas law to solve for n.

Once you get the no of moles (n) use the relation

moles = mass / molar mass

to get

molar mass = mass / moles
molar mass = mass/n (or, in your problem, 0.622/n)