# How do i identify an unknown gas knowing very little

1. Nov 9, 2009

### charizzardd

b]1. The problem statement, all variables and given/known data[/b]

I have to design a procedure to figure out what an unknown gas inside a syringe of known volume is. We are also given pressure transducers and have software(labview) that will allow us to graph voltage created by changing the volume of the syringe. I have no clue how to do this.

Is there some relationship between molar mass, and voltage? I have been messing around with ideal gas equation, boyles law, and maxwell relations but I still cant get anywhere with this.

Basically we need to design the procedure using only air, so that we can eventually do our procedure on an unknown gas sample in a syringe and identify the gas. Im not even looking for complete answers, maybe just some tips. How can I identify the gas knowing only volume and voltage created. I guess I can figure out the pressure as well using a bourdon gage or something, but that is it. Please help!

2. Relevant equations

Thermodynamic equations,
p=p(V,T) where p is pressure, V is volume, and T is temperature.

($$\Delta$$p=($$\partial$$p/$$\partial$$V)$$_{T}$$dV + ($$\partial$$p/$$\partial$$T)$$_{V}$$dT

*note all superscripts are subscripts, i dont klnow why it is coming in as super when i put it in as sub, anyway, they are just denoting that that variabvle is constant fro that partial derivative.

or maybe energy? I am also thinking that if i can graph the voltage, then perhaps I can find the current associated with that, Power=VI, which is in watts/s from here I can equate work and power, work being the change in internal energy as there is no temperature change. Well im sure there is, but it is negligable and therefore not counted. The fluid is being treated as an ideal gas, at constant pressure and mass.

maxwell equations

U=U(s,V):

$$\Delta$$U=($$\partial$$U/$$\partial$$s)$$_{V}$$dt + ($$\partial$$U/$$\partial$$V)$$_{s}$$dV

Then $$\Delta$$U=Q-W

W also = $$\int$$pdV where p is pressure and V is volume.
Perhaps I can find mass from here, and using ideal gas finding the numbe rof moles, and using it to find the molecular weight, and there for identifying the gas.

Hope someone can point me in the right direction!!!!

Last edited: Nov 10, 2009