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

In summary, the conversation is about calculating the net dipole moment of water using an equation found on the website provided. The equation is given as: "the net dipole moment =2(1.5)xcos(104.5/2)=1.84 D." The person asking the question has been getting the wrong answer and is seeking help to figure out what they are doing wrong. It is eventually revealed that they were using radians instead of degrees in their calculation.
  • #1
HelloCthulhu
151
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! :]
 
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  • #2
Have you tried to switch your calculator to DEG?
 
  • #3
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?
 
  • #4
But you know the difference between degrees and radians, do you?
 
  • #5
Oh, wow. Totally screwed that up. Changed 104.5 radians and now I've got 1.836. Thanks Borek! :D
 

What is the dipole moment for water?

The dipole moment for water is a measure of the separation of positive and negative charges in a molecule of water. It is also known as the electric dipole moment.

What is the direction of the dipole moment for water?

The direction of the dipole moment for water is from the positive end of the molecule, the hydrogen atoms, towards the negative end, the oxygen atom.

How is the dipole moment for water calculated?

The dipole moment for water is calculated by multiplying the distance between the two charges, the magnitude of the charges, and the cosine of the angle between the two charges.

What is the unit of measurement for dipole moment?

The unit of measurement for dipole moment is the Debye (D), which is equal to 3.33564 x 10^-30 coulomb meters (Cm).

Why does water have a dipole moment?

Water has a dipole moment due to the unequal sharing of electrons between the oxygen and hydrogen atoms. The oxygen atom is more electronegative, meaning it attracts electrons more strongly, resulting in a partial negative charge on the oxygen atom and a partial positive charge on the hydrogen atoms.

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