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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: s.p.q.r on July 26, 2007, 07:44:00 AM

Title: How Quickly Do Ideal Gases Expand?
Post by: s.p.q.r on July 26, 2007, 07:44:00 AM: Hi,

If I have 100 moles of an ideal gas at 25 degrees C and I heat it to 100 degrees C (373 Kelvins) How long would it take for it to reach its final size?

Cheers.
Title: Re: How Quickly Do Ideal Gases Expand?
Post by: AWK on July 26, 2007, 07:48:06 AM: Just time of heating
Title: Re: How Quickly Do Ideal Gases Expand?
Post by: s.p.q.r on July 26, 2007, 03:12:29 PM: So, if the container was already 100 degrees c, then the gas was put inside, how long would this take to expand?
Title: Re: How Quickly Do Ideal Gases Expand?
Post by: enahs on July 26, 2007, 03:17:25 PM: It will be under kinetic control due to diffusion.
Title: Re: How Quickly Do Ideal Gases Expand?
Post by: Borek on July 26, 2007, 04:31:50 PM: How much is a little bit? Question is too vague.

Perhaps my English fails me, but I don't think heat transfer and diffusion are the same thing... But if you replace diffusion with heat transfer in enahs answer it will be reasonable just as the one given by AWK ;)
Title: Re: How Quickly Do Ideal Gases Expand?
Post by: enahs on July 26, 2007, 04:51:04 PM: Quote from: Borek on July 26, 2007, 04:31:50 PM
Perhaps my English fails me, but I don't think heat transfer and diffusion are the same thing... But if you replace diffusion with heat transfer in enahs answer it will be reasonable just as the one given by AWK ;)

The last irritation of the question removed the heat transfer, as I read it anyway. In that instance, the gas can only fill up the volume of the container as fast as it can move; and thus controlled by the rate of diffusion. Maybe I misread the intent, but eh, whatever. ;D
Title: Re: How Quickly Do Ideal Gases Expand?
Post by: Borek on July 26, 2007, 05:34:42 PM: OK, I know what you mean... but I still don't think that's diffusion limited. Diffusion speed is limited by the collisions and random walk of the molecules; you don't have these when the gas is expanding.

As I understand the question you have gas in a closed expandable container and you heat it - so the speed of volume changes depends only on the heat transfer inside of the tank. But perhaps my understanding of the question was skewed by the fact, that I have tried to make sense out of it - so I assumed gas is in the container, as otherwise there will be no final volume...

Now, even if you put the gas into already heated container, it have to be heat up - as it is not stated what is the starting temperature of the gas. Jeez, the longer I try to make something out of it the worse it looks. Time to shut up :)