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So a toxic gas A contains 53.8% nitrogen and 46.2 % carbon. At 273 K and 1.01 x 10^5 Pa, 1.048 g of A occupies 462 cm^3. Determine the empirical formula of A, calculate the molar mass and determine the molecular structure.

I have trouble determining the molar mass. When I do it, I end up getting around 5.094 g/mol but accordingly the answer is supposed to be 51.9 g/mol. How do you get the latter answer?

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1) Ideal gas law. P = 101000 Pa. V = 0.000462 m3 (1 m3 = 1 000 000 cm3), R = 8..31 J K-1 mol-1, T = 273 K. 
We get n = 0.020568 mol.
To check, if you use instead STP then 1 mol gives you 0.0227 m (in booklet) --> 0.020568 mol gives you 0.0004667 m3, which is close to the given value of 462 cm3 so we are on the right track.

2) Use molar mass = mass / mol.
molar mass (gas) = 1.048 / 0.020568 = 50.95 g/mol. And a reminder that this is computed with the values given in the 2016 data booklet. If you use R = 8.314 J / K / mol, then answer is 50.98 g/mol. If you use 273.15 K (0°C) and R = 8.314 you get 51.0 g/mol.
 

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