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Select the correct statement...

Select the correct statement

A

`BF_3` and `NH_3 `have same dipole moment

B

dipole moment of `NH_3` is smaller than that of `BF_3`

C

`BF_3` molecule has a planar structure while the `NH_3` molecules is tetrahedral

D

the nitrogen atom has unshared pair of electrons while the boron atom has a free valence orbital

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question, we need to analyze each of the statements provided regarding BF3 (Boron Trifluoride) and Ammonia (NH3) and determine which one is correct. ### Step-by-Step Solution: 1. **Understanding the Structures**: - **BF3**: Boron trifluoride has a trigonal planar structure. The bond angles are approximately 120 degrees. Since BF3 is symmetrical, the dipole moments of the B-F bonds cancel each other out, resulting in a net dipole moment of zero. - **NH3**: Ammonia has a trigonal pyramidal structure due to the presence of a lone pair of electrons on the nitrogen atom. This lone pair causes the bond angles to be slightly less than 109.5 degrees (the ideal tetrahedral angle), and because of the asymmetry, NH3 has a net dipole moment that is not zero. 2. **Analyzing the Statements**: - **Statement 1**: "BF3 and Ammonia have the same dipole moment." - This is incorrect because BF3 has a dipole moment of zero, while NH3 has a non-zero dipole moment. - **Statement 2**: "The dipole moment of BF3 is less than that of Ammonia." - This is also incorrect. BF3 has a dipole moment of zero, which is less than the non-zero dipole moment of NH3. - **Statement 3**: "BF3 has a planar structure and Ammonia is a tetrahedral structure." - This statement is incorrect as well. While BF3 is indeed planar, NH3 is not tetrahedral; it is trigonal pyramidal. - **Statement 4**: "Nitrogen has an unshared pair of electrons and Boron has a free vacant orbital." - This statement is correct. Nitrogen in NH3 has one lone pair of electrons, and Boron in BF3 has an empty p-orbital that can accept electron pairs. 3. **Conclusion**: - The only correct statement is Statement 4: "Nitrogen has an unshared pair of electrons and Boron has a free vacant orbital." ### Final Answer: The correct statement is: **Statement 4** - "Nitrogen has an unshared pair of electrons and Boron has a free vacant orbital."
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