Dipole moment and net torque of an atom

In summary: So, in this case, the net charge on each atom would be q and -q respectively. In summary, the HCl molecule has a dipole moment of 3.4x10-30 C.m, with equal and opposite charges of q and -q on each atom respectively. The maximal torque it will experience in a 5.104 N/C electric field is 2.3x10-27 Nm, and the energy required to rotate it 45° from its equilibrium orientation is 6.74x10-28J.
  • #1
Parad0x88
74
0

Homework Statement


The HCl (hydrochloric acid) molecule has a dipole moment of about 3.4x10-30 C.m. The two atoms are separated by about 1.10-10 m. What is the net charge on each atom? What is maximal torque that this dipole will experience in a 5.104 N/C electric field? How much energy one would need to rotate one molecule 45o from its equilibrium orientation?

Homework Equations


A) Can't figure out which formula to use to find the net charge
B) τ = P X E
C) Not sure about this one: W = ΔU = U45° - U0° = - PE Cos45° - (- PE Cos 0°)

NOTE: For B, I am assuming that the initial angle is 0° to make my life easier since the information is not provided

The Attempt at a Solution


A) Can't figure out which formula to use to find the net charge

B) 3.4 X 10 -30 Cm χ 5 X 104 N/C = 2.3 X 10-27 Nm, or Joules

C) (-2.3 X 10-27J X cos 45°) + 2.3 X 10-27J
= -1.626 X 10-27J + 2.3 X 10-27J = 6.74 X 10-28J

Does that make sense for B and C? And could you give me any pointers for A?

Thank you!
 
Last edited:
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  • #2
I don't know what the rule is with bumping, but here it is, anyone has any idea for this problem?
 
  • #3
Do you know the formula for dipole moment?
 
  • #4
Pranav-Arora said:
Do you know the formula for dipole moment?

I tried to find it in my book, but the only formula I have is the one to find the torque, which I used in B, and the formula which I used in C

However, to find the charge in a dipole moment I do not seem to have the formula written down. I've browsed through my book but I don't seem to find it.

Edit: Heh just did a Wikipedia search: Dipole moment can be defined as the product of magnitude of charge & distance of separation between the charges (I didn't have that formula written down)

Knowing this, would question A be:

Dipole = Charge X Distance

3.4 X 10-30 Cm = Charge X 1 X 10-10 m

(3.4 X 10-30 Cm) / (1 X 10-10 m) = Charge (meters cancel out)

However, how can I differentiate to know whether I found the charge of which atom or the molecule?
 
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  • #5
Parad0x88 said:
However, how can I differentiate to know whether I found the charge of which atom or the molecule?

In dipole the charges are equal, so one of the charge will be q and the other -q.
 

1. What is dipole moment and how is it measured?

Dipole moment is a measure of the separation of positive and negative charges within a molecule or atom. It is measured in units of debye (D) and is calculated by multiplying the distance between charges by the magnitude of the charges. The larger the dipole moment, the more polar the molecule or atom is.

2. How does the dipole moment affect the polarity of a molecule or atom?

A dipole moment indicates the polarity of a molecule or atom. If the dipole moment is non-zero, the molecule or atom is polar and has a positive and negative end. If the dipole moment is zero, the molecule or atom is nonpolar and has no separation of charges.

3. What is net torque and how does it relate to dipole moment?

Net torque is the measure of the rotational force on an object. In the case of an atom or molecule, the dipole moment determines the strength of the net torque. A higher dipole moment means a stronger net torque, which means the object will rotate more easily in an electric field.

4. How is the net torque of an atom or molecule affected by its shape?

The shape of an atom or molecule can greatly affect its net torque. For example, a linear molecule with a high dipole moment will have a higher net torque than a similar molecule with a lower dipole moment. Additionally, the orientation of the molecule in an electric field can also affect the net torque.

5. Can the dipole moment and net torque of an atom or molecule change?

Yes, the dipole moment and net torque of an atom or molecule can change. This can happen through changes in the electron distribution or changes in the orientation of the molecule. Additionally, external factors such as temperature and pressure can also affect the dipole moment and net torque of an atom or molecule.

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