Coloumb's Law and Electric Dipoles question

[John Yi]

Homework Statement

1)HCl consists of one H and Cl atom separated by 0.127 nm, the bond length. The Cl atom has a partial charge of -0.177e and the H atom has a partial charge of +0.177e, where e = 1.602x10-19 C is the electron charge.

2)Now the HCl molecule is placed near a sodium ion Na+ with charge +1e. As shown in the figure, the distance between the Cl and Na atoms is d = 1.6 nm.

Homework Equations

I had finished question 1, but am stuck on question 2.

The Attempt at a Solution

I started with k(q1)(q2)/r^2 ----> (9x10^9) x (2.83554e-20) x (1.602e-19) / (1.727e-9)^2

I end up with an answer with 1.37e-11, but it is saying it is wrong. What am i doing incorrectly?

 

[gneill]

What are the questions associated with 1) and 2). What are you supposed to calculate?

The diagram referenced would be helpful: What are the relative positions of the charges? Is the Na ion on the axis of the dipole formed by the H and Cl atoms?

Note that fields and forces are vector quantities: they have both magnitude and direction. They also have units associated with them. Don't forget to include units on all results!

 

[John Yi]

Ah I am sorry. The question I am supposed to answer is :

What is the magnitude of the total force on the HCl molecule due to the Na+ ion |FHCl|?

 

[gneill]

You should make a sketch of the arrangement and draw in the force vectors operating on the H and Cl atoms due to the Na atom. Also indicate their X and Y components. Can you tell what the sum of those vectors will be from the sketch?