The boiling point of a substance indicate the strength of its intermolecular forces. The stronger the intermolecular forces the higher the boiling point. Compounds with weak intermolecular forces have low boiling points.
H2S has a relatively low boiling point of - 60.3 °C. This means that the intermolecular forces between H2S molecules are weak. These weak forces are not enough to hold H2S molecules together in a liquid or solid state at room temperature. Therefore , hydrogen sulfide exists as a gas at room temperature.
The weak intermolecular forces in H2S are due to its molecular structure. H2S is a polar molecule, meaning that it has a positive end ( the hydrogen atoms) and a negative end ( the sulphur atom ). However, the polarity of H2S is not very strong .This is because the electronegativity difference between hydrogen and sulphur is relatively small. The small difference in electronegativity results in a weak partial positive charge on the hydrogen atoms and a weak partial negative charge on the sulphur atom.
The weak polarity of H2S means that the intermolecular forces between H2S molecules are weak. This results in a low boiling point and the existence of H2S as a gas at room temperature.
