Solving the Piston Problem: Calculating Time for No Molecules Left

In summary, the conversation is about a person trying to determine the time at which no molecules will be left in a closed system with a frictionless piston. They have calculated the initial number of moles and the initial rate, but are unsure how to calculate the time when no molecules of a certain type will remain in the gaseous phase. They are looking for a solution that does not involve complex integration.
  • #1
mojo4king
10
0
Hello,
Piston question,i need to work out the time when no molecules are left in the gaseous system..
I have worked out the relative velocity..if i multiply that by the mean free path to get
the diffusion coefficient am i getting any closer to the answer?
I can work out the change in time using an equation involving collision frequency but i'm
guessing mean free path has to be involved somewhere..
This question had been bugging me for weeks!
Regards.
 
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  • #2
I've only just seen it and its already bugging me! Could you be more specific? Why is it a piston problem and not a diffusion problem?
 
  • #3
closed system,frictionless piston initially filled with gas molecules A, piston mass 100g,area 10cm2,10cm from bottom,pressure outside 1atm,temp. iniside system 900oC, i have already calculated the initial number of moles using pv=nrt...

Next using the collision flux multiplied by the area i have determined the initial rate.

Final question is how would i calculate the time after which no molecules of A will remain in the gaseous phase in the system (doesn't require complex integration).

Many thanks.
 
  • #4
Please quote the original question verbatim.
 

1. How do you solve the piston problem?

To solve the piston problem, you need to use the ideal gas law equation, PV = nRT, where P is the pressure of the gas, V is the volume, n is the number of moles of gas, R is the gas constant, and T is the temperature. By rearranging the equation, you can calculate the time it takes for all molecules to leave the piston.

2. What is the ideal gas law equation?

The ideal gas law equation is PV = nRT, where P is the pressure of the gas, V is the volume, n is the number of moles of gas, R is the gas constant, and T is the temperature. This equation is used to relate the physical properties of an ideal gas.

3. What is the significance of calculating the time for no molecules left in the piston?

Calculating the time for no molecules left in the piston is important because it helps us understand the behavior of gases in closed systems. It also allows us to predict when a certain amount of gas will completely leave a given space, which has practical applications in industries such as chemistry and engineering.

4. What factors affect the time for no molecules left in the piston?

The time for no molecules left in the piston is affected by several factors, including the initial number of moles of gas, the temperature, and the volume of the piston. Changes in these variables can alter the amount of time it takes for all molecules to leave the piston.

5. Can the ideal gas law be used for all gases?

No, the ideal gas law is only accurate for ideal gases, which are gases that follow certain assumptions such as having no intermolecular forces and occupying negligible volume. Real gases may deviate from the ideal gas law at high pressures and low temperatures.

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