Question

In the compound $PC{l}_k{F}_{5-k}$, the possible values of k are 0 to 5. Then the sum of all possible value of k for the compounds having zero dipole moment is:

Answer 1

Two molecules are possible.
a) $PC{l}_5$ k =5
b)$PC{l}_3{F}_2$ k = 3. Here, F occupies the axial position according to Bent's rule and Cl occupies the equatorial position.
In both dipole vector cancels each other and hence the dipole moment will be zero.
Sum = 5+3= 8