Chapter 12, Problem 51A

Interpretation Introduction

Interpretation:

Difference between temporary dipole and permanent dipole must be explained.

Concept introduction:

A molecule will be polar if the resultant of all bond moments in the molecule is non-zero.

Answer to Problem 51A

Permanent dipole is shown by polar molecule whereas temporary dipole is shown by non-polar molecule.

Explanation of Solution

A molecule might be non-polar in spite of having difference in electro negativity. In this case the vector sum of all the bond moments is zero. For example in BF₃ molecule the vector sum of any two bond moment is equal and opposite to the 3^rd bond moment. So they cancel each other.

In non-polar molecule dipole can be induced with the help of polar molecule. Then this is temporary dipole. For example in inert gas like He dipole moment can be induced in one atom which can induce surrounding atom and thus whole sample can be polarized which results in the generation of temporary dipole.

For permanent dipole the molecule should be polar which means the vector sum of all the bond moments is non-zero as those don’t cancel each other completely.

Conclusion

Permanent dipole is shown by polar molecule and temporary dipole is shown by non-polar molecule.