Question

Give reasons:(1) viscosity of a liquid decreases at high temperature.(2)H-F has lower boiling point as compared to H2O although fluorine is more electronegative than oxygen.(3) H-Cl has polar bond while Cl-Cl is non polar bond.

Answer 1

1) As temperature increases molecules move faster and attraction forces between them become weaker. Therefore, viscosity of a liquid decreases at high temperature.

2) F has more unshared electron pairs and is very electronegative. Therefore, H of another HF molecule can H-bond with it. Therefore, HF has lower boiling point compared to water.

3) Particles in Cl-Cl molecule have the same electronegativity. That is why, the bond between them is non-polar. H and Cl in H-Cl molecule have different electronegativity. Each of molecules attract other one with different force. Therefore, they have polar bond.