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# Finding the molar mass?

Reviewing back to older material from the semester and I am a little off going back to this. How do I find this answer?

An unknown gas has a density of 1.53 g/L at 1.00 atm and 30.6 C. What is the molar mass of the gas?

### 1 Answer

- 9 years agoFavorite Answer
the formula for finding density is D=PM/RT where P=pressure, M=molar mass, R=gas constant, and T=temperature in kelvins. Rearrange this equation to find M and you get: M=DRT/P

Before plugging in values, convert 30.6C to Kelvins by adding 273, and you will get 303.6K.

So plug in your values: [(1.53g/L)(0.08206 Lxatm/molxK)(303.6K)] divide by 1.00atm.

Liters will cancel, atm will cancel, and kelvins will cancel. Your answer will be in g/mol, which is what you want since that is what molar mass is always in when it comes to dealing with gas laws.

You answer should be: 38.1g/mol.

Good luck!!!! Hope this helped.