Question

The correct order of increasing dipole moments is:

• A. $HI<HBr<HCl<HF$
• B. $HBr<HI<HCl<HF$
• C. $HI<HBr<HF<HCl$
• D. $HF<HCl<HBr<HI$

Answer 1

The correct option is A $HI<HBr<HCl<HF$

Dipole moment occurs due to the difference in electronegativity between the two chemically bonded atoms.
Among $Cl,F,Br$ and $I$ the order of increasing electronegativity is $I<Br<Cl<F$.
In HF, the fluorine atom will attract electrons more towards itself producing a polar molecule and hence, a dipole. Since, fluorine is the most electronegative, the electronegativity difference with hydrogen, and hence the dipole moment, will be the most. As electronegativity difference decreases, dipole moment also decreases.
So, the order of dipole moment will be $HI<HBr<HCl<HF$