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I have recently learned about the Ideal Gas Equation and I have this doubt.....suppose I am in a closed container filled with a gas of fixed volume and definite amount of moles. I am assuming myself as a point mass, not having any effect on the gas and just observing the process taking place. What if I increase the temperature to higher and higher values until infinity ? Would there be an infinite amount of pressure on me as well ? I tried doing this by taking initial pressure as 0 and then realized the final pressure would also be zero. I realize that I might be mixing up misunderstood notions and sound crazy but help would be appreciated !

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  • $\begingroup$ Pressure is exerted on macroscopic objects such as the wall of the container. The particles do not experience pressure but instead experience collisions with other particles, at some frequency and with some average kinetic energy of the particles involved. $\endgroup$ Oct 8 at 17:34
  • $\begingroup$ @KarstenTheis but doesn't that mean that the collisions a particle will face will increase linearly as pressure exerted on outside increases..................? $\endgroup$
    – Sia Evelyn
    Oct 8 at 18:16
  • $\begingroup$ The only two things that increase collisions are higher particle speeds (higher temperature) and higher particle concentration (governed by n and V). A change in outside pressure, if it compresses the gas, will decrease V while keeping n constant, so that will indeed increase the number of collisions. $\endgroup$ Oct 8 at 19:37
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Yes, of course. Rearrange the ideal gas law into the form $$\frac{P}{T} = \frac{nR}{V}.$$ Since by construction the volume and number of moles is fixed, the right-hand side of the equation is constant, so the pressure increases linearly with the temperature in your situation.

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  • $\begingroup$ $n$ is the amount of substance, not "number of moles or "amount of moles". $\endgroup$
    – andselisk
    Oct 9 at 11:57
  • $\begingroup$ Sure, but you may want to add that the volume would have to be infinite (or the density zero) for the pressure to be zero at a finite T. $\endgroup$
    – Buck Thorn
    Oct 9 at 15:11
  • $\begingroup$ @andselisk, in this case it must be the number of moles because the ideal gas constant $R$ is represented on a molar basis. $\endgroup$ Oct 10 at 12:03
  • $\begingroup$ @a-cyclohexane-molecule "Number of moles" shouldn't be used at all. Not only this term doesn't make sense semantically, but also IUPAC explicitly recommends against applying it. $\endgroup$
    – andselisk
    Oct 10 at 12:51
  • $\begingroup$ @andselisk, thank you for the link and information. I disagree that 'number of moles' does not make semantic sense---it is certainly logically accurate in the sense that 'amount of substance measured in moles' is the 'number of moles of substance', but you do make a good point that it is now against current convention. $\endgroup$ Oct 10 at 18:48

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