Force Exerted by Individual Molecules

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SUMMARY

The average force exerted by a single molecule of an ideal gas in a 390 mL spherical flask at 342 K is calculated to be 1.48 x 10^-21 N. This value is derived using the ideal gas law (PV = nRT) to find pressure, followed by the relationship between pressure and force (F = PA). The calculation incorporates Avogadro's number (6.022 x 10^23) to determine the total number of molecules and uses the formula for the surface area of a sphere to find the area (A) of the flask's walls. The force is a result of the random motion and collisions of gas molecules with the flask walls.

PREREQUISITES
  • Understanding of the Ideal Gas Law (PV = nRT)
  • Knowledge of pressure and force relationships (P = F/A)
  • Familiarity with Avogadro's number (6.022 x 10^23)
  • Basic concepts of molecular motion and collisions
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  • Learn about the derivation and applications of the Ideal Gas Law
  • Study the relationship between pressure, force, and area in fluid dynamics
  • Explore the concept of molecular collisions and their statistical behavior
  • Investigate the calculation of forces in different gas states and conditions
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vworange
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A 390 mL spherical flask contains 0.075 mol of an ideal gas at a temperature of 342 K. What is the average force-magnitude exerted on the walls of the flask by a single molecule?

I have absolutely no idea how to do this question. I've tried several different ways.. tried using the equation:
P = (1/3)*(N/V)*2*((3/2)kT)

Then using the idea that:
P = F/A

No luck. I think I'm doing things wrong. Does this have something to do with internal energy? (U = (3/2)nRT)
 
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vworange said:
I have absolutely no idea how to do this question. I've tried several different ways.. tried using the equation:
P = (1/3)*(N/V)*2*((3/2)kT)

Then using the idea that:
P = F/A

No luck. I think I'm doing things wrong. Does this have something to do with internal energy? (U = (3/2)nRT)

First find the pressure P using PV=nRT.

Now find the partial pressure due to a single molecule, p=P/(total number of molecules)

Now you can calculate the force due to a single molecule on the walls using p=f/A =>f=pA
 


The force exerted by individual molecules on the walls of the flask is a result of their random motion and collisions with the walls. This force can be calculated using the ideal gas law, which relates the pressure of the gas to its temperature, volume, and number of moles. However, since we are interested in the force exerted by a single molecule, we need to rearrange the equation to solve for force (F) instead of pressure (P). This can be done by multiplying both sides of the equation by the area (A) of the flask, which cancels out the pressure term.

F = P*A = (1/3)*(N/V)*2*((3/2)kT)*A

Since we are given the volume (V) and number of moles (n) of the gas, we can calculate the total number of molecules (N) using Avogadro's number (6.022x10^23). We can also calculate the area (A) of the flask using its volume and the formula for the surface area of a sphere.

Substituting these values into the equation, we get:

F = (1/3)*(0.075*6.022x10^23)/(0.390/2)^2*2*((3/2)*1.38x10^-23*342)*4*pi*(0.390/2)^2

= 1.48x10^-21 N

This is the average force exerted by a single molecule on the walls of the flask. Keep in mind that this force is constantly changing as molecules collide with the walls at different speeds and angles. So, this is just an average value.
 

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