Question

Pheromones are chemical substances secreted by members of a species to stimulate a response in other individuals of the same species. for example, certain pheromones are secreted by females of a species to attract males for mating. the percent composition of eicosene (280 g/mol), a compound similar to the japanese beetle mating pheromone, is 85.63% c and 14.37% h. determine its molecular formula.

Answer 1

The percent composition of eicosene (280 g/mol) is 85.63% c and 14.37% h.
The number of C atoms would be:
percentage * eicosene weight/ carbon weight
85.63% * 280g/mol /  12g/mol= 19.98= 20

The number of H atoms would be: 
percentage * eicosene weight/ carbon weight
14.37% * 280g/mol /  1g/mol= 40.23= 40

The compound made of 20 carbon and 40 hydrogen, so it should be C20H40