Why Water H2O is liquid while hydrogen sulfide is gas even both Oxygen and sulphur belong to same group?

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 Recall that it is the molecular weight and extent of intermolecular forces which determine physical states( solid, liquid and gas) of substances.  Order of Intermolecular forces strength in substances is :

Solids>liquid>gases

When we look at molecular weight , it seems water would be in gaseous state and hydrogen sulfide be in liquid state. But here in case of water , water has hydrogen bonding . Hydrogen bonding is limited to  three highly electronegative atoms ( F, O and N). In water H2O, Hydrogen is attached to 2nd highest electronegative atom i.e O of periodic table.Hence water is having relatively strong intermolecular forces in form of hydrogen bonding. On other hand Hydrogen sulphide is having simple dipole-dipole interaction. Order of intermolecular forces in strength is 

Hydrogen Bonding> dipole-dipole forces> London forces


Hydrogen-bonding-in-water-h2O
 Hydrogen bonding among water H2O molecules

On other hand Hydrogen sulphide is having simple dipole-dipole interaction. Order of intermolecular forces in strength is 

Hydrogen Bonding> dipole-dipole forces> London forces

Dipole-dipole-interaction-among-H2S-molecules
Dipole-dipole interaction among hydrogen sulphide H2S molecules



Comments

  1. UnknownOctober 20, 2021 at 1:51 PM

    Easy to understand

    ReplyDelete
  2. UnknownOctober 20, 2021 at 3:57 PM

    Very informative 👍
    Your all chemistry lectures are easy to understand.thank you

    ReplyDelete
  3. UnknownOctober 20, 2021 at 3:58 PM

    Thanks again for your lectures of chemistry

    ReplyDelete

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