Which one of the following molecules is the most polar?
1) acetic acid
2) acetaldehyde
3) ethylene
4) ethane
a is the most polar by far.
To determine the polarity of a molecule, we need to consider its molecular shape and the electronegativity difference between its atoms.
First, let's determine the molecular shape of each molecule:
1) Acetic acid (CH3COOH) - The acetic acid molecule has a bent shape due to the presence of a lone pair on the oxygen atom.
2) Acetaldehyde (CH3CHO) - The acetaldehyde molecule has a trigonal planar shape with a slight bent due to the presence of a lone pair on the oxygen atom.
3) Ethylene (C2H4) - The ethylene molecule has a planar shape with a double bond between the carbon atoms.
4) Ethane (C2H6) - The ethane molecule has a tetrahedral shape with single bonds between the carbon atoms.
Next, let's consider the electronegativity difference between the atoms in each molecule:
1) Acetic acid - The oxygen atom is more electronegative than the carbon and hydrogen atoms, creating a polarity between the oxygen and the rest of the molecule.
2) Acetaldehyde - The oxygen atom is more electronegative than the carbon and hydrogen atoms, creating a polarity between the oxygen and the rest of the molecule.
3) Ethylene - Ethylene does not contain any highly electronegative atoms, so it is nonpolar.
4) Ethane - Ethane does not contain any highly electronegative atoms, so it is nonpolar.
Based on the molecular shapes and electronegativity differences, we can conclude that acetic acid and acetaldehyde are polar molecules while ethylene and ethane are nonpolar molecules.
Therefore, the most polar molecule among the options is either acetic acid or acetaldehyde.