Finding atomic diameter from molecular diffusion proportionality

Click For Summary

Homework Help Overview

The discussion revolves around determining the diameter of an argon atom using the relationship between diffusion (D) and pressure (p), specifically given that the product Dp equals 2. Participants are exploring the implications of this relationship within the context of molecular diffusion.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants are attempting to relate the molar mass of argon to its atomic mass and are questioning the lack of provided values for volume, temperature, and pressure. There is discussion about the dimensional consistency of the equation and the meaning of the dimensionless number "2". Some participants suggest that temperature might be assumed to be constant, while others express uncertainty about the completeness of the problem statement.

Discussion Status

The discussion is ongoing, with participants raising valid points about the assumptions needed to approach the problem. Some have provided insights into the relationship between diffusion and pressure, while others are questioning the clarity of the problem statement and the necessary conditions for solving it.

Contextual Notes

There is a noted lack of specific values for temperature, volume, and pressure, which are critical for solving the problem. Participants are also considering the implications of assuming room temperature and the potential discrepancies in units related to the given information.

ProPatto16
Messages
323
Reaction score
0

Homework Statement



Find the diameter of one atom of argon given that Dp = 2 where D is diffusion and p is pressure.

The Attempt at a Solution



molar mass of argon is 40g/mol
using that for one atom can find mass in kgs.
but that's its!

im not given V, T or p. can put V in terms of d so that gives me one. need 2 so i can solve for the last one.

the relevant equation seems to be
$$Dp=\frac{1}{\pi d^3\sqrt{m}}(\frac{2kT}{\pi})^\frac{3}{2}$$

good luck finding d.
 
Physics news on Phys.org
The diffusion constant has units m^2/s, pressure has units N/m^2 = kg /(m s^2). The product of both cannot be a dimensionless number ("2").
I think there is something missing here.

Unrelated: if you just need T, room temperature is a good value.
 
It's not a constant. Diffusion D and pressure p are inversely proportional. The info I'm given is as pressure increases the product of diffusion and pressure is 2. So the 2 is the x in D=x/p hence dimensionless. I'm fairly sure that this means T is constant.
Sorry probably a poor worded question.
Given a figure of a graph of Dp vs p for argon and it's a line parallel to x-axis with the value 2.
Question says find diameter of argon. So I don't have particular values for p and D either...
 
Hmm but I see what you mean... It still needs units... But even then with units it won't make a difference.

And I think there's something missing too.

And I actually have the answer as d=3.1*10^-10m out of the book but that corresponds to a T of about 330K
but there's no way to find T with the info given..
 
ProPatto16 said:

Homework Statement



Find the diameter of one atom of argon given that Dp = 2 where D is diffusion and p is pressure.
Is that the full, exact problem statement?
If yes, I think you really have to assume that it happens at room temperature, and I still doubt that the units match.
 

Similar threads

Replies
4
Views
1K
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
Replies
2
Views
4K
Replies
6
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K