The water molecule consists of two hydrogen atoms and one oxygen atom. Since the

Question

The water molecule consists of two hydrogen atoms and one oxygen atom. Since the oxygen atom has a higher electronegativity than the hydrogen atom, the side of the molecule with the oxygen atom has a partial negative charge.

Part A) Assume that the partial negative charge on the oxygen atom is Q1 = -1.008 x 10^-19 C. What is the magnitude of the charge Q2 on each hydrogen atom?

Part B) The water molecule forms an angle, with the hydrogen atoms at the tips and the oxygen atom at the vertex. Assume the angle at the oxygen atom is theta = 104.6 degrees and the distance between the oxygen and the hydrogen atoms is d = 99.8 x 10^-9 m. Calculate the magnitude of the net electrostatic force on the oxygen atom. Use the charges from the previous problem.

Explanation / Answer

A)
As the entire atom is electrically neutral, Therefore the magnitude of the positive charge on each of the two hydrogen atoms must be half the negative charge on the oxygen atom -

Magnitude of charge Q2 on Each Hydrogen atom = 1.008 x 10^-19 C / 2
Magnitude of charge Q2 on Each Hydrogen atom = 5.04 * 10^-20 C

B)
Force between two charges (H2 & O) -
Force = k * Q1 * Q2 / r^2
Force = 8.9 * 10^9 * 1.008 x 10^-19 * 5.04 * 10^-20 /(99.8 x 10^-9 )^2
Force = 4.54 * 10^-15 N

Net Electrostatic Force on the oxygen atom = 2 * F * cos(104.6/2)
Net Electrostatic Force on the oxygen atom = 2 * 4.54 * 10^-15  * cos(52.3)
Net Electrostatic Force on the oxygen atom = 5.55 * 10^-15 N

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