The correct option is A 1.617×10−10 esu
We know, resulatnt dipole moment can be calculated using
R = √P2+Q2+2PQcosθ
where R = μH2O = Resultant dipole moment
P = μOH = dipole moment of OH bond
So, μH2O = √μ2OH+μ2OH+2μ2OHcosθ
Put up the values,
1.85 D = √2μ2OH(1+cos105o)
On solving, we get μOH = 1.52 D
Now 1 D = 10−18 esu cm
So, μOH = 1.52×10−18 esu cm
Also, μOH = δ×d
where δ = partial charge on oxygen atom
d = bond distance of O−H bond = 0.94×10−8 cm
δ = 1.52×10−180.94×10−8 = 1.617×10−10 esu