Can someone please help! A neutral water molecule (H_2 O) in its vapor state has
ID: 2307287 • Letter: C
Question
Can someone please help!
A neutral water molecule (H_2 O) in its vapor state has an electric dipole moment of magnitude 6.2 Times 10^-30 C.m. How far apart are the molecule's centers of positive and negative charge? If the molecule is placed in an electric field of 1.5 Times 10^4 N/C, what maximum torque can the field exert on it? How much work must an external agent do to rotate this molecule by 180 degree in this field, starting from its fully aligned position, for which theta = 0? Compare this energy to a typical thermal energy when the molecule is part of a gas at a temperature 400 K.Explanation / Answer
Dipolemoment P = 6.2 x10 -30 Cm
Charge q = 2e = 2x1.6 x10 -19 C
We know P = q xL
From this separation of the center of positive and negative charges L = P /q
L = (6.2 x10 -30 Cm)/(2x1.6 x10 -19 C)
= 1.9375x10 -11 m
(b).Electric field E = 1.5 x10 4 N/C
Maximum torque = PE
= ( 6.2 x10 -30 Cm)(1.5 x10 4 N/C)
= 9.3x10 -26 Nm
(c).Work done W = PE [ cos 0 - cos 180 ]
= PE [ 1-(-1)]
=2PE
= 1.86x10 -25 J