## Gas Problem SOMEONE HELP ME!!!!!!!!!!!!!!!!!!!!!!!!!!!111111

**Anonymous**

Find the volume of a gas at -30 celcius and 0.75 atm if it occupies a volume of 255L at 40.0 celcius and 1.25 atm.

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Anonymous| 18 October 2004 - 9:37amFrom your post title, I thought maybe you had severe indigestion... roll

Anonymous| 18 October 2004 - 12:04pmThe equation you are looking for is:

[b][color=red]PV = nRT[/color][/b]

Where:[color=#EFEFEF]SPACER[/color]P = Pressure (in Pa)

[color=#EFEFEF]Where:SPACER[/color]V = Volume (in L)

[color=#EFEFEF]Where:SPACER[/color]T = Temperature in Kelvin

[color=#EFEFEF]Where:SPACER[/color]n and R are constants.

So plug in your (converted) values into the equation, work out the constant value is (it doesn't matter exactly what n anr R are, just what nR is as a constant), then plug in the values at the other temperature, rearrange the equation and find the volume.

Anonymous| 18 October 2004 - 7:49pm## allan_chemist- Gas question

So are you saying to find out either n or R first.

Then combine n and R to form nR and plug it into the equation with the second temperature and rearrange the equation to find the volume?

Anonymous| 18 October 2004 - 8:06pmJust ignore n and R.

Pretend the equation is [b][color=red]PV=cT[/color][/b], where c is a constant.

[size=7](Of course, if you are asked to work out the number of moles of the gas, then use R = 8.314472 J/K/mol, but I doubt you'll need that.)[/size]

Anonymous| 19 October 2004 - 10:49pmPV=nRT p is pressure that must be in atmospheres or something and volume has to be in liters. R is always .0821 and T has to be in kalvin which is celcius plus 273. n is the number of moles that your trying to find.

Anonymous| 19 October 2004 - 10:55pmfor that one you could also use P1V1T2=P2V2T1 so you say that your first pressure is .75 and your first volume is N and your T2 or second tempurate all though it goes on the left side is 40 + 273 to get it in kalvin. Then on the right your second pressure is 1.25 and second volume is 255 then your first temperate is -30 + 273. so then you have .75 times n times 40+273 = 1.25 times 255 times -30 + 273.

Anonymous| 20 October 2004 - 6:22amYou should probably see a doctor. :roll:

Anonymous| 20 October 2004 - 12:09pm[quote="Dudeman1"]for that one you could also use P1V1T2=P2V2T1 so you say that your first pressure is .75 and your first volume is N and your T2 or second tempurate all though it goes on the left side is 40 + 273 to get it in kalvin. Then on the right your second pressure is 1.25 and second volume is 255 then your first temperate is -30 + 273. so then you have .75 times n times 40+273 = 1.25 times 255 times -30 + 273.[/quote]

Indeed, that method is better, as you don't need to do any conversions (except ?C into K) to get the correct answer.

Also, just out of interest, you say [b]Kalvin[/b] in your post. Is that just a mistake on your part, or is this another US/UK English difference I didn't know about? (We spell it [b]Kelvin[/b])

Anonymous| 20 October 2004 - 10:21pm[quote]Also, just out of interest, you say Kalvin in your post. Is that just a mistake on your part, or is this another US/UK English difference I didn't know about? (We spell it Kelvin)

You know I've wondered the same thing, I have also seen it wriiten as both kelvin and kalvin in different textbooks. I believe it is a color/clour situation.[/quote]

Anonymous| 21 October 2004 - 1:52amAmerica uses Kelvin :roll: