Explain why `H_2O` is a liquid but` H_2S` is a gas at room temperature.

Explanation

Since atmoic size of oxygen is less then sulphur, and electronegativity of oxygen is more than sulphur, water shows inter-molecular hydrogen bonding but hydrogen sulphide does not. As such a large number of water molecules are associated with each other to form to form a cluster of molecules. Thus a large amount of energy is required for their separation. This energy is not available at room temperature. Thus water is a liquid and hydrogen sulphide is a gas at room temperature.

Due to extensive hydrogen bonding in `H_2 O` and its absence in `H_2 S`, boiling point of water is much more than the boiling point of `H_2 S`.