Question

Explain ${{\text{H}}_{\text{2}}}\text{O}$ is liquid but ${{\text{H}}_{\text{2}}}\text{S}$ is gas.

Answer 1

Hint: The physical state of a compound is mainly determined by the arrangement of molecules and kind of intramolecular interaction (chemical bonds) present in between the molecules.
Hydrogen bonds are stronger bonds than van der wall’s forces, since hydrogen bonds are regarded as an extreme form of dipole-dipole interaction.

Complete answer:
 ${{\text{H}}_{\text{2}}}\text{O}$ Molecules are polar molecules. ${{\text{H}}_{\text{2}}}\text{O}$ Molecules are associated through intermolecular hydrogen bond formed between oxygen atom of one water molecule and hydrogen atom of other water molecule due to a difference between electronegativities. However ${{\text{H}}_{\text{2}}}\text{S}$ is a nonpolar molecule, these molecules are associated through weak van der wall’s force of attraction. Hence ${{\text{H}}_{\text{2}}}\text{O}$ is liquid and ${{\text{H}}_{\text{2}}}\text{S}$ is gas at normal temperature.

Additional information:
Hydrogen bond is an electrostatic attractive force present between partially positive charged hydrogen atoms of a polar molecule and a highly electronegative atom carrying partial negative charge of the same molecule or in a different molecule. Hydrogen bonds are of two types; intermolecular hydrogen bond and intramolecular hydrogen bond. Strength of hydrogen bond depends upon the electronegative atom, more the electronegativity of atom stronger the bond.
Van der Waals forces are weak, non-directional and non-valence force of attraction among neutral molecules.

Note:
Intramolecular hydrogen bond formed between hydrogen atom and an electronegative atom $\text{(F,O and N)}$ both present in the same molecule while intermolecular hydrogen bond formed in between two polar molecules.
Hydrogen bond forms in polar covalent compounds. It is not formed in an ionic compound.