d) Incorrect. CCl4 is a tetrahedral molecule.
Each of the bonds is polarized toward the chlorine atom. Adding together
any two bond
dipoles gives a subtotal sum halfway between them directed away from the
central carbon atom. Adding together the other two bond
dipoles gives a second subtotal sum halfway between them directed away
from the central carbon atom. These two subtotal sums are
exactly opposite each other (tail-to-tail) and will therefore cancel each
other out making the molecule nonpolar. CH2Cl2
is also a tetrahedral
molecule. Each of the C-Cl bonds is polarized toward the chlorine
atom and the C-H bonds are polarized toward the carbon atom. Adding
together the two C-Cl bond dipoles gives a subtotal sum halfway between
them directed away from the central carbon atom. Adding
together the two C-H bond dipoles gives a subtotal sum halfway between
them directed toward the central carbon atom. These two subtotal
sums do not cancel each other out (in fact, they reinforce each other)
so the molecule is polar. CHCl3 is also a tetrahedral
molecule. Each of
the three C-Cl bonds is polarized toward the chlorine atom while the C-H
bond is polarized toward the carbon atom. Adding together two
C-Cl bond dipoles gives a subtotal sum halfway between them directed away
from the central carbon atom. Adding together the third C-Cl
bond and the C-H bond dipoles gives a subtotal sum which won't cancel out
the other subtotal sum (since the combination is different) thus
the molecule is polar.