Which one of the following substances would have the lowest melting point? a) cl2 b) hi c) h2o d) ccl4

chlorine molecule.

Explanation:

The melting point of a substance depends upon the intermolecular interactions present between the molecules of the substance.

Stronger the interactions higher the boiling point and vice versa.

In case of polar compounds the interactions are stronger than non polar compounds.

water (H₂O) is a polar compound and has intermolecular hydrogen bonds between molecules, which makes its melting and boiling point high.

HI is also a polar molecule and has dipole dipole interactions.

CCl₄ has polar bonds but the molecule is non polar due to net zero dipole moment.

Cl₂ is a completely non polar molecule and has only weak london dispersion forces between molecules, thus it has lowest melting point among the given molecules.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.