molecular weight of a compound

[Foad]

How do we calculate the molecular weight of a compound?

[omar_chemical]

Thank You

[peterjames23_2007]

your question is vague !! i hope you mean to say a petroleum compound??????
which donot have constant composition hence no exact mol.wt but has avg
if u simply mean a mol.wt of a compound
1) split compound into its elements
2) multiply No.of each elements with its mol.wt
3)addition of which gives you the molwt of compound
EX: H2SO4
it's really simple H2=2(NO.of H2 molecule)*1(mol.wt of H2)
S = 1(NO.of S molecule)*32(mol.wt of S)
O4= 1(NO.of O molecule)*16(mol.wt of S)
= 98 which is mol.wt of H2SO4
if you mean mixture here is procedure
1) u will know the composition of given mixture/mixtures of compound
2)which shall be sum upto 100 if given in % or 1 if given in fractions (wt or mol. if they sumup to 1/100 they information given is wrong)
3) now just put it the formula below
mol.wt (avg) = (mol.wt)1*x1+.......+(mol.wt)n*xn
(mol.wt)n = mol.wt of component n

[OMID1351]

I think th MWof Hydrocarbons is very important for simulation. But for HC heavier than Naphtha ( FBP > 170 C) we cannt use GC method
Is there any method for measuring heavy HC(FBP>170 C) ?

[peterjames23_2007]

hi omidi 1351,
well this is intellectually wise question.......
as far as my knowledge is concerned ( s iam still an undergraduate student ).
HC heavier than naptha (FBP > 170 C) most of the time they exists in mixture rather than pure components . for precise calculations no other method exists rather than sticking to experimental studies ( calculating exact composition of each component,column chromatography is widely used for this purpose) and exact mol.wt is determined as i gave in above comment . if u want a rudimentary simulation (if composition of heavier HC is very low ) olefin >C5 would be a pretty good guess (it's only thumb rule ) .
i hope this work's out ?????????

[nskvc]

Thank You

[waleedalattar]

thank's