Question

Which one of the following substances would have the lowest melting point? A) Cl2 B) HI C) H2O D) CCl4

Answer 1

In the given examples, Cl2 and CCl4 are non-polar and held by covalent bonds. HI and H2O are polar molecules and held by ionic bonds.

Since covalent bonds are weaker than ionic bonds, Cl2 or CCl4 must have the lowest melting points. Among the two, Cl2 has a lower molecular mass than CCl4, hence Cl2 must have the lowest melting point.

Ans A) Cl2

Answer 2

Answer:

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.