Calculating Net Dipole Moment for Water - What Am I Doing Wrong?

Click For Summary

Discussion Overview

The discussion revolves around the calculation of the net dipole moment for water, focusing on the application of the dipole moment equation and the potential errors in calculation methods. Participants explore the technical aspects of the calculation and the use of different tools for trigonometric functions.

Discussion Character

  • Technical explanation, Debate/contested, Homework-related

Main Points Raised

  • One participant cites an equation for the net dipole moment of water and expresses confusion over consistently obtaining an incorrect result.
  • Another participant suggests checking the calculator settings to ensure it is in degree mode.
  • A participant mentions using an iPhone app and Google's scientific calculator, questioning whether the initial answer of 1.84 D was correct.
  • There is a clarification about the difference between degrees and radians, which is acknowledged by the original poster.
  • The original poster later corrects their calculation after realizing the angle was in radians, resulting in a new value of 1.836 D.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the initial calculation methods, but there is agreement on the importance of using the correct angle measurement in calculations.

Contextual Notes

The discussion highlights potential limitations in understanding the distinction between degrees and radians, which may affect the accuracy of calculations.

HelloCthulhu
Messages
150
Reaction score
3
Greeting PF!

http://chemwiki.ucdavis.edu/Physical_Chemistry/Atomic_Theory/Dipole_Moments

On the website above, I found an equation for the dipole moment of water:

"...the net dipole moment =2(1.5)xcos(104.5/2)=1.84 D."

I understand how to calculate the bond dipole. But after calculating for the net dipole, I keep getting the same wrong answer: -1.20606

Please tell me what I'm doing wrong! Thank you so much for your assistance! :]
 
Chemistry news on Phys.org
Have you tried to switch your calculator to DEG?
 
I'm using an iPhone app. It has a tab for trig where I found cos(, so I don't think I have to switch modes. I've also used Google's scientific calculator and received the same answer. Was your answer 1.84?
 
But you know the difference between degrees and radians, do you?
 
Oh, wow. Totally screwed that up. Changed 104.5 radians and now I've got 1.836. Thanks Borek! :D
 

Similar threads

What Does a Dipole Moment of 1.85 in Halomethanes Indicate?
  • · Replies 1 ·
Replies
1
Views
8K
Effect of different magnetic fields on a magnetic dipole
  • · Replies 25 ·
Replies
25
Views
2K
Why is there a discrepancy in the calculated dipole moment of a water monomer?
  • · Replies 12 ·
Replies
12
Views
38K
Undergrad The direction of electric dipole moment of water molecule
  • · Replies 7 ·
Replies
7
Views
4K
How to calculate the dipole moment of the spherical shell?
  • · Replies 1 ·
Replies
1
Views
8K
Calculating Jupiter's Magnetic Dipole Moment Using a Dipole Approximation
  • · Replies 6 ·
Replies
6
Views
4K
How Do You Calculate the Magnetic Field Due to an Iron Disc's Dipole Moment?
  • · Replies 3 ·
Replies
3
Views
2K
Finding the dipole moment of a molecule in an electric field
  • · Replies 3 ·
Replies
3
Views
7K
Electric dipole moment for a uniformly charged ring
  • · Replies 10 ·
Replies
10
Views
11K
How can I calculate the z-component of the magnetic field using the dot product?
  • · Replies 19 ·
Replies
19
Views
3K