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Calculate the bond dipoles for ammonia molecule to predict the polarity of ammonia molecule.
Accepted Answer
To calculate the bond dipoles for an ammonia molecule and predict its polarity, follow these steps:
1. Determine the molecular geometry: Ammonia has a trigonal pyramidal molecular geometry with three N-H bonds and one lone pair of electrons on the nitrogen atom.
2. Calculate the bond dipole moments: The bond dipole moment (μ) is a vector that points from the less electronegative atom to the more electronegative atom. For the N-H bond, the electronegativity difference between nitrogen and hydrogen is 3.0 - 2.1 = 0.9. Using the formula μ = q × d, where q is the charge and d is the distance between the charges, we can estimate the bond dipole moment to be around 0.33 D (1 D = 3.336 × 10^-30 C m).
3. Determine the direction of the bond dipoles: The bond dipoles point from hydrogen to nitrogen for each N-H bond.
4. Calculate the net dipole moment: The net dipole moment is the vector sum of the individual bond dipole moments. In ammonia, the three bond dipoles partially cancel each other out due to the trigonal pyramidal geometry. However, there is a small net dipole moment pointing away from the nitrogen atom, resulting in a polar molecule.
Therefore, the polarity of the ammonia molecule is due to the net dipole moment, which is a consequence of the difference in electronegativity between nitrogen and hydrogen and the molecular geometry.
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