Question

Use the electronegativity table given in Figure 2-2 to predict which bond in each of the following pairs is more polar, and indicate the direction of bond polarity for each compound.

a)${\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{-}\mathbf{CI}$or $\mathbf{CI}\mathbf{-}\mathbf{CI}$

b)${\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{-}\mathbf{H}$or$\mathbf{H}\mathbf{-}\mathbf{CI}$

c)$\mathbf{HO}\mathbf{-}{\mathbf{CH}}_{\mathbf{3}}$or ${\mathbf{\left(}{\mathbf{CH}}_{\mathbf{3}}\mathbf{\right)}}_{\mathbf{3}}\mathbf{Si}\mathbf{-}{\mathbf{CH}}_{\mathbf{3}}$

d)${\mathbf{H}}_{\mathbf{3}}\mathbf{C}\mathbf{-}\mathbf{Li}$or$\mathbf{Li}\mathbf{-}\mathbf{OH}$

Short answer

a) ${\mathrm{H}}_3\mathrm{C}-\mathrm{CI}$is more polar.

The direction of bond polarity is as follows:

b) $\mathrm{H}-\mathrm{CI}$is more polar.

The direction of bond polarity is as follows:

c) $\mathrm{HO}-{\mathrm{CH}}_3$is more polar.

The direction of bond polarity is as follows:

d) $\mathrm{Li}-\mathrm{OH}$is more polar.

The direction of bond polarity for both the molecules is as follow;

Step-by-step solution

Bond polarity and its direction

If the electronegativity difference between the bond is high then a covalent bond is polar. If the electronegativity difference between the bond is zero then the bond is non-polar and it has a zero dipole moment.

The direction of bond polarity is from the less electronegative atom toward the more electronegative one.

identification of more polar bond

Among ${\mathrm{H}}_3\mathrm{C}-\mathrm{CI}$and $\mathrm{CI}-\mathrm{CI}$electronegativity difference between$\mathrm{C}-\mathrm{CI}$bonds is high therefore${\mathrm{H}}_3\mathrm{C}-\mathrm{CI}$is more polar than $\mathrm{CI}-\mathrm{CI}$bonds. Also, we can say that the electronegative difference between $\mathrm{CI}-\mathrm{CI}$bonds is zero therefore it is non-polar.

The direction of bond polarity for both the molecules is as follow;

Subpart (b)

$\mathrm{H}-\mathrm{CI}$bond is more polar than ${\mathrm{H}}_3\mathrm{C}-\mathrm{H}$as electronegativity difference between$\mathrm{H}-\mathrm{CI}$is high as compared to $\mathrm{C}-\mathrm{H}$bond. The direction of bond polarity for both the molecules is as follow;

Subpart c)

$\mathrm{HO}-{\mathrm{CH}}_3$bond is more polar than ${\left({\mathrm{CH}}_3\right)}_3\mathrm{Si}-{\mathrm{CH}}_3$. Because the electronegativity difference between the$\mathrm{O}-\mathrm{H}$bond is more than that of$\mathrm{Si}-\mathrm{C}$bond. The direction of bond polarity for both the molecules is as follow;

Step 5:Subpart (d)

$\mathrm{Li}-\mathrm{OH}$bond is more polar than${\mathrm{H}}_3\mathrm{C}-\mathrm{Li}$ bond.As electronegativity difference between$\mathrm{Li}-\mathrm{O}$bond is higher than that of$\mathrm{C}-\mathrm{Li}$ bond.

The direction of bond polarity for both the molecules is as follow;