How Do You Calculate the Degrees of Freedom (DOF) for CO2

[Atlas14]

I need help with my Chemistry homework and I am being asked to calculate the degrees of freedom for CO2, but we have not yet learned what DOF even is. Would anyone be able to help me? Thanks

 

[The Last Conformist]

The number of degrees of freedom would depend on the temperature ...

... but what silly sort of teacher gives homework about something you don't even know what it is? I'd go complain about that if I were you.

 

[Irish Caesar]

The number of degrees of freedom would depend on the temperature ...

...or pressure...

 

[Atlas14]

Well it is our Chem Lab assignment, but we haven't learned about it yet in either lab or lecture yet.

No temperature is given, it simply says calculate the DOF of CO2.

 

[Perfection]

The number of degrees of freedom would depend on the temperature ...

True, but I think we can generally assume that were gonna only see translational and rotational because that's what you see at room temperature.

In that case it would be 5. Two rotational axes, and three translational directions.

 

[Atlas14]

True, but I think we can generally assume that were gonna only see translational and rotational because that's what you see at room temperature.

In that case it would be 5. Two rotational axes, and three translational directions.

I just tried 5, and the program said Incorrect answer. And now Im out of tries. But the rest of the problems depend on me finding that one out...

 

[puglover]

Isn't this the second time you've asked for homework help?

 

[Atlas14]

Isn't this the second time you've asked for homework help?

The first time was in math, my worst subject, and now my chem teacher is being a jerk and assigning graded homework that has not been taught yet, not even close to being taught.

 

[Perfection]

I just tried 5, and the program said Incorrect answer. And now Im out of tries. But the rest of the problems depend on me finding that one out...

That's utter jerkness. The other options are probably 7 or 3. I'd just complain.

 

[Atlas14]

That's utter jerkness. The other options are probably 7 or 3. I'd just complain.

Supposedly 5 was the number of vibrational degrees of freedom since it is a linear molecule. The total I think is 9 dof since each atom has 3. Since it is triatomic, it equals 9. Thanks for the help everyone

 

[pboily]

... but what silly sort of teacher gives homework about something you don't even know what it is? I'd go complain about that if I were you.

A teacher who wants his/her students to realize that learning is more than just rote stuff?

 

[MrCynical]

Supposedly 5 was the number of vibrational degrees of freedom since it is a linear molecule

I really don't think that's right. For a linear molecule the number of vibrational modes is 3N - 5, where N is the number of atoms in the molecule. CO2 would therefore only have 4 vibrational degrees of freedom, not 5. CO2 would also have 2 rotational modes as it is linear, and 3 translational modes, for the total of 9.

So the answer's correct, but the explanation there is wrong.

The number of degrees of freedom would depend on the temperature ...

I've only seen this from a chemical perspective, but why is temperature relevant? It would affect the partition functions, yes, but not the number of degrees of freedom.

 

[Atlas14]

I really don't think that's right. For a linear molecule the number of vibrational modes is 3N - 5, where N is the number of atoms in the molecule. CO2 would therefore only have 4 vibrational degrees of freedom, not 5. CO2 would also have 2 rotational modes as it is linear, and 3 translational modes, for the total of 9.

So the answer's correct, but the explanation there is wrong.



I've only seen this from a chemical perspective, but why is temperature relevant? It would affect the partition functions, yes, but not the number of degrees of freedom.

Crap you're right. The vibrational DOF is 3N-5 which equals 4 vib dof, I can't remember what my final answer was. I may have put down four...