Explain how to determine if the compound, boron tribromide, BBr3 is an ionic, polar or non-polar compound. Include a Lewis Structure in your answer, as well as a clear explanation. (b) Is the B-Br bond polar or nonpolar? (circle one) Explain how to determine if the B-Br bond in the following compound, BBr3 is ionic, polar or nonpolar. (c) Does this compound, boron tribromide dissolve in water? Yes or No and explain Show work please
The Correct Answer and Explanation is:
To determine whether boron tribromide (BBr₃) is ionic, polar, or nonpolar, we follow a few key steps: drawing the Lewis structure, analyzing bond polarity, and assessing the overall molecular polarity.
(a) Lewis Structure and Molecular Polarity:
Start by drawing the Lewis structure for BBr₃:
- Boron (B) has 3 valence electrons.
- Bromine (Br) has 7 valence electrons, and there are 3 Br atoms.
Total valence electrons = 3 (B) + 3 × 7 (Br) = 24 electrons.
Structure:
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Br — B — Br
Each Br atom forms a single bond with the central B atom. Boron has only 6 electrons around it, which is an exception to the octet rule and is acceptable for elements like B. Each Br completes its octet with lone pairs (not shown above for simplicity).
The molecular shape is trigonal planar, and because all three B-Br bonds are equivalent and 120° apart, their dipoles cancel out.
Conclusion: The molecule is nonpolar overall, despite having polar bonds.
(b) Is the B-Br bond polar or nonpolar?
Answer: Polar
Explanation: To determine the bond polarity, compare the electronegativity values:
- Boron: ~2.0
- Bromine: ~2.8
The difference is about 0.8, which indicates a polar covalent bond. The electrons are shared unequally, with the bromine being more electronegative and pulling the bonding electrons closer.
However, since the BBr₃ molecule is symmetrical, the individual dipoles of the B–Br bonds cancel out, making the molecule nonpolar overall.
(c) Does BBr₃ dissolve in water?
Answer: Yes
Explanation: BBr₃ is a reactive covalent compound. It hydrolyzes (reacts with water) rather than just dissolving. When mixed with water, it forms boric acid (H₃BO₃) and hydrobromic acid (HBr):
Reaction:
BBr₃ + 3H₂O → B(OH)₃ + 3HBr
This reaction releases hydrogen bromide, making the solution acidic. Though BBr₃ is nonpolar as a molecule, its reactivity with water allows it to effectively “dissolve” by chemical reaction, not simple solvation.
Summary:
(a) BBr₃ is a nonpolar covalent compound.
(b) Each B–Br bond is polar due to electronegativity difference.
(c) BBr₃ reacts with water, so it does dissolve, forming acids.
