What information must a chemist have to determine the molecular formula for a compound?

1 Answer
May 31, 2018

Answer:

Well, for a start the chemist must have the #"empirical formula" #...

Explanation:

And what is the #"empirical formula"#...? It is the simplest WHOLE NUMBER ratio defining constituent atoms in a species. And thus the #"empirical formula"# for #CH_4#, #C_2H_6#, and #C_3H_8#, are #CH_4#, #CH_3#, and #C_3H_8# respectively...With me? Combustion analysis of organic compounds is nowadays routine....#"% by mass"# with respect to carbon, hydrogen, nitrogen, may be readily acquired...and this allows determination of the empirical formula..

And then some determination of molecular mass is obtained…the #"molecular formula"# is a whole number MULTIPLE of the #"empirical formula..."#...i.e.

#"molecular formula"-=nxx"empirical formula"#

And of course #n# #"MAY EQUAL"# #1#..

See here for a representative problem....