Question

When bonded, the hydrogen atoms have their electron taken by Oxygen atom, which gives them a partial positive charge of E. The oxygen, therefore, has a net negative charge of -2e. The distance between oxygen and hydrogen is 0.9584 Angstrom. FIND the net force on the oxygen atom. ( please explain them in details with given information )

Answer 1

The force extered on the oxygen atom by each hydrogen atom, from Coulomb's law, is given by :

F = ( 1 / 4_o ) ( e x 2e ) / d², in magnitude,

where, e = 1.6 x 10^-19 C is the electronic charge,

d = 0.9584 Angstrom = 9.584 x 10^-11 m is the distance between two atoms,

and, ( 1 / 4_o ) = 9 x 10⁹ S.I. is permittivity constant.

Hence, F = (  9 x 10⁹ ) x 2 x ( 1.6 x 10^-19 / 9.584 x 10^-11 )² N ~ 5 x 10^-8 N.

We know, there is an 105^o angle between the H - O - H bond in a water molecule.

Hence, net force on the oxygen atom is :

( F² + F² + 2F² cos 105^o )

= 2 x F x ( 1 + cos 105^o )

= 2 x 5 x 10^-8 x ( 1 + cos 105^o ) N

~ 6.087 x 10^-8 N.