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Questions and Answers
Which of the following best describes a polar molecule?
Which of the following best describes a polar molecule?
What determines whether a molecule with polar covalent bonds is polar or non-polar?
What determines whether a molecule with polar covalent bonds is polar or non-polar?
In a bond dipole, what does the arrow point toward?
In a bond dipole, what does the arrow point toward?
Which of the following molecules is non-polar, despite having polar covalent bonds?
Which of the following molecules is non-polar, despite having polar covalent bonds?
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What is the primary factor that affects whether a molecule is soluble in water?
What is the primary factor that affects whether a molecule is soluble in water?
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If a molecule has a trigonal pyramidal shape, and contains a Nitrogen atom, it is likely to be:
If a molecule has a trigonal pyramidal shape, and contains a Nitrogen atom, it is likely to be:
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A tetrahedral molecule composed of four different atoms is typically:
A tetrahedral molecule composed of four different atoms is typically:
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When will a Trigonal planar molecule be non-polar?
When will a Trigonal planar molecule be non-polar?
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Study Notes
Molecular Polarity
- VSEPR shapes determine if a molecule is polar or non-polar.
- Water (H₂O) has polar covalent bonds and is a polar molecule.
- Carbon tetrachloride (CCl₄) has polar covalent bonds but is a non-polar molecule.
- Molecular polarity does not apply to ionic bonds.
Defining Bond Polarity
- Molecular polarity is the sum of the molecule's bond polarity vectors.
- Bond polarity is determined by identifying electronegativities.
- Partial charges (δ+) and (δ−) indicate electronegativity differences. A higher electronegativity value means an atom attracts electrons more strongly.
- The larger the electronegativity difference, the more polar the bond.
- Bond dipoles show the direction of polarity, an arrow that points to the more electronegative atom.
Determining Molecular Polarity
- Determine the direction of polarity for each bond.
- Draw the resulting dipoles.
- Consider bond dipoles as vectors.
- For non-polar molecules, the bond polarities cancel each other out due to symmetry or equal and opposite pulls on electrons.
- For polar molecules, the bond polarities do not cancel and a net dipole is observed.
Additional Factors
- Presence of polar covalent bonds may or may not make a molecule polar.
- Presence of non-polar covalent bonds may or may not make a molecule polar, depending on the shape of the molecule.
- Examine the molecule's shape using VSEPR theory to determine polarity.
- Examples: CO₂, CH₄, H₂O have different polarities depending on their structure/shape.
Examples and Practice Problems
- Examples: NH₃ (polar), BF₃ (non-polar), PH₃ (polarity?).
- Practice determining the polarity of various molecules given their structures.
- Workbook #11 is a valuable resource for additional practice problems.
General Rules
- Trigonal pyramidal molecules (N, P) are generally polar.
- Trigonal planar (double bond) are generally non-polar.
- Tetrahedral (all same atoms) are generally non-polar with 3 same atoms and 1 different are generally polar.
- Linear (like CO₂) are generally non-polar.
- Polar molecules are often made more easily polar, by having atoms with different electronegativities.
Importance and Applications
- Polarity plays a crucial role in how detergents clean clothes.
- Polar or non-polar nature affects interactions between molecules. (think Lipids and Bile Acids)
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Description
Test your understanding of molecular polarity, bond polarity, and the VSEPR theory. This quiz will cover key concepts such as the electronegativity differences and how they affect the polarity of molecules like water and carbon tetrachloride. Answer questions to see how well you grasp these important chemistry principles.
