Chapter U2, Problem 16STP

Interpretation Introduction

Interpretation:

The polar molecule/s needs to be identified.

Concept introduction:

The bonds in polar molecules are polar due to electronegativity difference between the atoms which are bonded together.

Answer to Problem 16STP

Correct Answer: ${\text{NH}}_{\text{3}}$ and ${\text{CH}}_3\text{OH}$

Explanation of Solution

Reason For Correct Option :

1) ${\text{CH}}_3\text{OH}$ is a polar molecule with one O-H bond, this configuration allows the formation of hydrogen bonds with other methanol molecules.

2) ${\text{NH}}_{\text{3}}$ is a polar molecule due to electronegativity differnce between N and H atoms. A lone pair of electron on N in this molecule tends to form one hydrogen bond with other ammonia molecule.

Conclusion

Reason for incorrect Option:

${\text{CCl}}_{\text{4}}$ : All the C-Cl bonds in carbon tetrachloride molecule are polar, but the overall molecule is non-polar because the molecule has symmetrical shape and dipole moments get cancelled out.

${\text{C}}_{\text{2}}{\text{H}}_{\text{6}}$ : Some small amount of polarity which is generated is being cancelled due to symmetrical structure. Therefore Ethane is a non polar molecule. Also, the electronegtivity difference between C and H is not significant.