A) A hydrocarbon is made up of 85.71% carbon and 14.29% hydrogen. Work out the empirical formula of the substance b) if the relative molecular mass Is 42, find the molecular Formula of this hydrocarbon

A) A hydrocarbon is made up of 85.71% carbon and 14.29% hydrogen. Work

1.	A) A hydrocarbon is made up of 85.71% carbon and 14.29% hydrogen. Work out the empirical formula of the substance b) if the relative molecular mass Is 42, find the molecular Formula of this hydrocarbon
Answer» tion:AS with all these PROBLEMS, we assume (for simplicity) 100⋅g of UNKNOWN compound.And thus there are 85.7%×100⋅g12.011⋅g⋅mol−1 with respect to CARBON, i.e. 7.14⋅mol⋅C And 14.3%×100⋅g1.00794⋅g⋅mol−1 with respect to hydrogen, i.e. 14.1⋅mol⋅H .And thus the empirical formula , the simplest whole number ratio that defines constituent elements in a SPECIES is CH2 .Now the molecular formula is alway a whole number multiple of the empirical formula :empirical formula×n = molecular formula So (12.011⋅g⋅mol−1+2×1.00794⋅g⋅mol−1)×n=84⋅g⋅mol−1.So n=6 , and molecular formula = 6×CH2 = C6H12