Chemistry Problems

[Asian]

A gas has a density of 2.857 g/l at STP. The pressure is dropped by 20.0 kpa in order to change its density to 2.000 g/l, what must be the new temperature to achieve this lower density.

 

Any suggestions on how to start this problem is needed.

[danzman]

Hmm.. That is a tough one without the mass or volume of the gas. IF you assume 1mole and 22.4L you could get it with ease.

PV=nRT

100*22.4=n*8.3145*273.15 (since STP = 100kpa and 273.15K)

n=1.01 or about 1, thus there is one mole of gas.

With this you can set up the other side of the equation

80*V=1*8.3145*T

{80*V=8.3145*T}

Since you know that the new density is 2 and the mass will stay the same you can get the Volume.

2=64/X

X=32L

Plug it back into the equation and you get

80*32=8.3145*T

2560=8.3145*T

T=307.89584

Someone who was a little better at linear algebra than me could plug the original two equations into a matrix and tell you what the possible answers could be without assuming that it was ideal and that its volume was 22.4…. Come to think of it there must be the better way to do this. What is this for? GenChem or Physical chem.? Let me know what the answer is.

[Asian]

k thanks, that was the right answer when we checked in class

[danzman]

Cool..the sun even shines on a dogs ass every once in a great while..