Zangetsu Posted May 7, 2016 Report Share Posted May 7, 2016 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? Reply Link to post Share on other sites More sharing options...
Hassan76 Posted May 7, 2016 Report Share Posted May 7, 2016 (edited) maybe your approximations are different.Or missed an error of ten. Edited May 7, 2016 by Hassan76 Reply Link to post Share on other sites More sharing options...
kw0573 Posted May 7, 2016 Report Share Posted May 7, 2016 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 m3 (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. 1 Reply Link to post Share on other sites More sharing options...
Msj Chem Posted May 8, 2016 Report Share Posted May 8, 2016 (edited) Maybe these videos will help: Edited May 8, 2016 by Msj Chem Reply Link to post Share on other sites More sharing options...
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