Question

The bond angle and dipole moment of water respectively are:
A) ${{109.5}^{o}}$,1.84D
B) ${{107.5}^{o}}$, 1.56D
C) ${{104.5}^{o}}$,1.84D
D) ${{102.5}^{o}}$,1.56D

Answer 1

Bond angle is considered as the angle which is formed between the two covalent bonds which originate from the same atom. The angle of torsion for the four atoms bonded together in a chain is the angle between the plane formed by the first three atoms and the other plane formed by the last three atoms. The bond length increases with the decrease in the bond angle.

Complete answer:
The dipole moment arises in the system because of the charge separation present in it. They can arise in the covalent as well as in the ionic bonds. It determines the polarity of the chemical bond which is formed between the two atoms in the molecule.
The bond angle of water is ${{104.5}^{o}}$ this so because of the presence of two lone pairs of electrons in the molecule. The bond pair and the lone pair cause repulsion and the bond angle gets more so that the molecule gets stabilised. Now the condition of dipole moment arises in water molecules because of the electronegative oxygen present in it as it is more electronegative than hydrogen atom. The oxygen tends to pull the shared electrons towards itself thereby increasing the electron density around itself. Due to this the electric dipole moment vector is formed with the partial negative charge on the oxygen atom. There are two hydrogen oxygen bonds in the molecule so the dipole moment of the molecule will be the resultant vertical vector projection of the individual diagonal dipole vectors. So the answer is 1.84D.
Hence,the correct option is C.

Note: The dipole moment of the single bond in the polyatomic molecule is called the bond dipole moment. It is the vector quantity which has magnitude and direction as well. It is denoted with a small arrow with its tail on the negative center and the head on the positive center.