Polarity Practice Worksheet - Solutions - Free Printable

To determine which compound in each pair is more polar, we need to consider two main factors:
1. Electronegativity Differences: The greater the difference in electronegativity between the atoms in a bond, the more polar that bond is.
2. Molecular Geometry: The shape of the molecule determines if the individual bond dipoles cancel each other out or add up to create a net dipole moment.

Let's break down each pair:

1) Methyl chloride (CH₃Cl) vs. Methyl bromide (CH₃Br)
* Analysis: Both molecules have a similar tetrahedral shape. The difference lies in the halogen atom attached to the carbon. Chlorine (Cl) is more electronegative than Bromine (Br).
* Reasoning: Because Chlorine pulls electrons more strongly than Bromine, the C-Cl bond is more polar than the C-Br bond. This creates a stronger overall dipole moment in methyl chloride.
* Conclusion: Methyl chloride is more polar.

2) Water (H₂O) vs. Hydrogen sulfide (H₂S)
* Analysis: Both molecules have a bent shape. The central atom is Oxygen in water and Sulfur in H₂S.
* Reasoning: Oxygen is significantly more electronegative than Sulfur. This means the O-H bonds are much more polar than the S-H bonds. Additionally, Oxygen is small enough that its lone pairs create a strong repulsion, maintaining a distinct bent shape that enhances the polarity.
* Conclusion: Water is more polar.

3) Hydrochloric acid (HCl) vs. Hydroiodic acid (HI)
* Analysis: Both are linear diatomic molecules.
* Reasoning: We compare the electronegativity of Chlorine (Cl) and Iodine (I). Chlorine is much higher on the periodic table and is more electronegative than Iodine. Therefore, the difference in electronegativity between Hydrogen and Chlorine is greater than between Hydrogen and Iodine.
* Conclusion: Hydrochloric acid (HCl) is more polar.

4) Bromoacetylene (C₂HBr) vs. Chloroacetylene (C₂HCl)
* Analysis: Both are linear molecules with a triple bond between carbons. The difference is the halogen attached (Br vs Cl).
* Reasoning: Similar to question 1, Chlorine is more electronegative than Bromine. The C-Cl bond will have a larger dipole moment than the C-Br bond. Since the rest of the molecule is identical, the one with the more polar bond is the more polar molecule.
* Conclusion: Chloroacetylene is more polar.

5) Methanol (CH₃OH) vs. Diethyl ether [(CH₃)₂O]
* Analysis: Methanol contains an O-H group, while Diethyl ether has an oxygen bonded to two carbons (C-O-C).
* Reasoning: The O-H bond is highly polar because Hydrogen is bonded directly to a highly electronegative Oxygen atom. This allows for hydrogen bonding, which is a very strong dipole interaction. In diethyl ether, the oxygen is bonded to carbons, which are less electronegative than hydrogen in this context (or rather, the C-H bonds don't create the same strong dipole as O-H). The O-H bond makes methanol significantly more polar.
* Conclusion: Methanol is more polar.

6) Acetone [(CH₃)₂CO] vs. Propanol (C₃H₈O)
* Analysis: Acetone has a carbonyl group (C=O). Propanol has a hydroxyl group (O-H).
* Reasoning: While the C=O bond in acetone is polar, the O-H bond in propanol is capable of hydrogen bonding. Hydrogen bonding creates a much stronger dipole and higher polarity than a simple carbonyl dipole. Generally, alcohols (like propanol) are more polar than ketones (like acetone) of similar size due to the hydrogen bonding capability.
* Conclusion: Propanol is more polar.

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Final Answer:
1) Methyl chloride (CH₃Cl)
2) Water (H₂O)
3) Hydrochloric acid (HCl)
4) Chloroacetylene (C₂HCl)
5) Methanol (CH₃OH)
6) Propanol (C₃H₈O)