Question

TRUE/ FALSE

Assuming that the effect of bond energy is more important than the effect of electronegativity, the substance HBr is expected to be a stronger acid than the substance HF.

Answer 1

The statement is true.

F is more electronegative than Br, and if the only electronegativity factor is considered, HF would be stronger than HBr. But actually, HF is a weak acid. Hence, there is a competing factor.

The size of the halogens changes more dramatically than their electronegativities as you go up and down the group.

The F^- ion is very small compared to the Br^- ion, so negative charge is concentrated on this small F^- spherical particle.

The H and F atoms are comparable size. The HF bond length is very small and hence the bond energy is high. So that HF is a weak acid.