help (1 Viewer)

[riya03]

Could someone plz explain how to find the molecular formula from the question -

0.015 mol of a hydrocarbon has a mass of 0.63 g. calculate the molar weight of hydrocarbon and suggest a possible molecular formula for the hydrocarbon.

the molar weight is 42 g/mol, but how do i find the molecular formula?

 

[thongetsu]

mole = mass / molar mass

0.015 = 0.063 / M
M = 0.063 / 0.015
my molar weight was 4.2g :S

 

[Omnipotence]

mole = mass / molar mass

0.015 = 0.063 / M
M = 0.063 / 0.015
my molar weight was 4.2g :S

Lol molar weight is g/mol.

 

[ibbi00]

I'm not sure you need/can find out the molecular formula of the hydrocarbon based on this information.

 

[riya03]

The molar weight is correct. According to the answers, the m.f is C3H6

 

[ibbi00]

Well then maybe u typed the question wrong?

 

[riya03]

sorry, its 0.63

any help on how to find the m.f?

 

[ibbi00]

You trial and error pretty much. If it's a hydrocarbon then it obviously must have carbon atoms in it. I would have approached the question by dividing the molar mass if the hydrocarbon by the molar mass of a single carbon atom. i.e, 42/12.01 = 3.497... So you assume there's 3 carbon atoms and the rest must be hydrogen. If it's a hydrcarbon then it must be an alkene, alkane or alkyne. So you start adding hydrogen atoms accordingly until u get the answer.