Video: Applying Knowledge of Bond Polarity and Molecular Polarity

For statements I and II, state for each if they are true or false. I) A molecule of carbon tetrachloride, CCl₄, is nonpolar. II) The four bonds in CCl₄ are identical and the molecule has a tetrahedral structure. If both are true, state if II is a correct explanation for I.

03:04

Video Transcript

For statements one and two, state for each if they are true or false. I) A molecule of carbon tetrachloride, CCl₄, is nonpolar. II) the four bonds in CCl₄ are identical and the molecule has a tetrahedral structure. If both are true, state if II is a correct explanation for I.

Carbon tetrachloride is an example of an alcohol halide, otherwise known as a haloalkane. This is the displayed formula for carbon tetrachloride. Statement I suggests carbon tetrachloride is nonpolar. A nonpolar molecule is one with no net dipole or one where the dipole is very, very small. In order to assess whether carbon tetrachloride is polar, we need to look at the individual bond polarities and the atom electronegativities.

Carbon has an electronegativity of 2.55, while chlorine has and electronegativity of 3.16. This means that chlorine has a greater tendency to attract electrons toward itself than carbon does. So chlorines in carbon tetrachloride are delta negative while the carbon is delta positive. This generates a dipole for each bond. We need to see how these are arranged in space to see whether carbon tetrachloride is polar overall.

A molecule of carbon tetrachloride is tetrahedral. The four dipoles from the four CCl bonds all point outwards from the carbon atom. Because of the symmetry of the tetrahedral structure. Whenever we rotate around the axis for any carbon–chlorine bond, we can move the other three chlorines into equivalent positions. This is true for any of the carbon–chlorine bonds. Meaning that all of the carbon–chlorine bonds are equivalent. What happens is, because all these bonds are equivalent and because of the nature of the symmetry of a tetrahedral molecule, all the dipoles cancel out and CCl₄ is nonpolar.

So statement I is true. Statement II says that the four bonds in CCl₄ are identical and the molecule has a tetrahedral structure. This is exactly what we’ve just shown. So statement II is also true. Finally, since both are true, we need to say whether II is a correct explanation for I. Statement II brings up the two factors that we use to prove that carbon tetrachloride is nonpolar. The fact that the bonds are identical, and the molecule has a tetrahedral structure. So therefore, it is true that II is a correct explanation for I.

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.