[lisast42]

I am studying for a test on Monday and I have a problem that I am stuck on.  I was wondering if anyone can help me with the solution.  I know that the answer is 234.2 ml but again I need help getting to that answer, here is the problem:

   A gas at STP occupies 96ml.  What will its volume be at 380torr and 60 degrees C?

If anyone can help I would greatly appreciate it.

I was setting up the problem as follows, but it is not working out and I don't know what I am doing wrong

96ml(380torr x 22.4)/333K

[sjb]

What is STP?

Basically, apply pV = nRT twice, given that n is a constant.

[lisast42]

STP= Standard Temperature and Pressure.
I am sorry but I dont understant pv=nRT we actually were not taught that way in class we were taught to find V1;V2;T1 and T2 and so on that is the only way I am familiar with....sorry, but thank you.

[sjb]

So you know that p1 x v1 = p2 x v2 for a given sample of gas at constant temperature? Also that ^p1/_t1 = ^p2/_t2 at constant volume for a given sample, or that ^v1/_t1 = ^v2/_t2 at constant pressure?

Combine these and you can see that ^{p1 x v1}/_t1 = ^{p2 x v2}/_t2 for a given sample of gas, and so rearranging that ^{p1 x v1 x t2}/(_{t1 x p2}) = v2

Does this help?

By "what is STP", I was more after the actual values (preferably in torr and °C, as that's the units of your other data points are, but note you'll have to convert into K for the calculation above)

[lisast42]

Ok so I did have it set up the right way, however I must be putting my values in the wrong spots this is what I have
v1=96ml
v2=?
t1=60 degrees C=333K
t2=?
P1=380 torr
p2 =?

so V2= (380torr x 96ml)/333K = 109.5 (which is not the right answer, I have moved the numbers around in every possible combination and I can't arrive at the right answer of 234.2ml)

[sjb]

Ok so I did have it set up the right way, however I must be putting my values in the wrong spots this is what I have
v1=96ml
v2=?
t1=60 degrees C=333K
t2=?
P1=380 torr
p2 =?

so V2= (380torr x 96ml)/333K = 109.5 (which is not the right answer, I have moved the numbers around in every possible combination and I can't arrive at the right answer of 234.2ml)

t1 is your initial temperature, which is not 333K. p1 is your initial pressure, not 380 torr. Both of these are given by the fact your sample is initially at STP. t2 is 333K, and p2 is 380 torr.

What is STP in terms of temperature and pressure?

[lisast42]

What is STP in terms of temperature and pressure?

If I am understanding the question correctly I believe STP=22.4 (Liters?) I think.

Thank you for all your help, I need to leave to go to work now, but I still would appreciate any help I will check back later.

[sjb]

No, 22.4 litres is the *volume* of a mole of gas at STP. What is the pressure at STP? What is the temperature? I hesitate to give you a link as things are currently a bit ambiguous, and ironically, STP is not just one set of figures (though the two most recognized sets do not have that much difference). Is there a definition in a textbook you can use?

(It's possible I can guess which STP you mean by the fact you've mentioned 22.4 litres, but I don't want to pre-empt stuff here)

[lisast42]

Ok I finally understood what you where asking me and I figured it out

96ml x 760torr/380torr x 333K/273K = 234.2ml.

Thank you so much.