Sort these substances by boiling point

[transgalactic]

HCOOH
C_4H_10
C_2H_6
CH_2
H_2they all are polar covalent
except H_2 which is pure covalent
how to sort them??

 

[Bacat]

Stronger bonds will have higher boiling points. Look in your chemistry book about the strengths of different types of bonds.

 

[transgalactic]

it depends on the electro negativity value difference between two
substance
but here there are more then two ellements
and more then one appearence
of the same ellement

??

 

[Simon_Moore]

Boiling point is a measure of the amount of thermal energy that has to be provided in order to overcome whatever intermolecular forces exist between the molecules of the material when it is in liquid form.

Therefore, look at each of the species in question and work out which ones would likely have a notable number of (a) dipole-dipole attraction, (b) instantaneous-dipole/induced-dipole attractions, (c) hydrogen bonding, and which would only be likely to exhibit the weaker van der Waals type intermolecular forces.

For example, you would expect H₂O water to have a higher boiling point than CH₃OH methanol because water has a higher dipole moment, and also a greater tendency for hydrogen bond formation (two hydrogen atoms with partial positive charge per molecule, as opposed to only one in methanol).

If you take a look through the 5 compounds you have listed you should be able to rank them in this way.