For each of the following pairs of molecules, determine which is most polar

For each of the following pairs of molecules, determine which is most polar: C2H4 or C2H5OH, C2H6 or CH3OCH3, CCl4 or CF4, H2O or H2S. C2H4: C2H5OH, C2H6: CH3OCH3, CCl4: CF4, H2O: H2S.

The Correct Answer and Explanation is:

Let’s analyze each pair to determine which molecule is more polar:

1. C2H4 (ethene) vs. C2H5OH (ethanol):
   • C2H4 (ethene): This is a nonpolar molecule due to its symmetric structure and equal sharing of electrons between the carbon atoms.
   • C2H5OH (ethanol): Ethanol is a polar molecule because of the hydroxyl group (OH). The oxygen in the OH group has a partial negative charge, while the hydrogen has a partial positive charge. This creates a dipole moment in the molecule.
   More polar: C2H5OH (ethanol) is more polar due to the polar OH group.
2. C2H6 (ethane) vs. CH3OCH3 (dimethyl ether):
   • C2H6 (ethane): Ethane is a nonpolar molecule because it is symmetrical and the electrons are evenly shared between the two carbon atoms.
   • CH3OCH3 (dimethyl ether): Dimethyl ether has an oxygen atom, which is electronegative and creates a dipole between the oxygen and the two methyl groups (CH3). The oxygen atom pulls electron density away from the carbon atoms, creating a dipole moment.
   More polar: CH3OCH3 (dimethyl ether) is more polar due to the dipole created by the oxygen atom.
3. CCl4 (carbon tetrachloride) vs. CF4 (carbon tetrafluoride):
   • CCl4 (carbon tetrachloride): This is a nonpolar molecule because it has a symmetrical tetrahedral structure, and the dipoles of the four C-Cl bonds cancel each other out.
   • CF4 (carbon tetrafluoride): Similar to CCl4, CF4 is also a tetrahedral molecule. However, the fluorine atoms are more electronegative than chlorine, which creates dipoles that cancel out symmetrically.
   More polar: Neither is more polar. Both are nonpolar due to their symmetrical tetrahedral structure, despite the difference in electronegativity.
4. H2O (water) vs. H2S (hydrogen sulfide):
   • H2O (water): Water is highly polar. Oxygen is more electronegative than hydrogen, creating a significant dipole moment in the molecule.
   • H2S (hydrogen sulfide): Although sulfur is less electronegative than oxygen, it still creates a dipole in the H2S molecule. However, the dipole moment is weaker than in water due to sulfur’s lower electronegativity.
   More polar: H2O (water) is more polar due to the stronger electronegativity difference between oxygen and hydrogen.

Summary:

• C2H4 vs. C2H5OH: C2H5OH (ethanol) is more polar.
• C2H6 vs. CH3OCH3: CH3OCH3 (dimethyl ether) is more polar.
• CCl4 vs. CF4: Neither is more polar; both are nonpolar.
• H2O vs. H2S: H2O (water) is more polar.