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Gas Laws

1) A combustion cylinder (containing a fixed number of moles of gas initially at 9.00atm ) with a moveable piston is maintained at a constant temperature changes volume from 2.00 L to 6.0 L. Determine the change in pressure during this action.

P1 = 9.00 atm
V1 = 2.00 L
P2 = ?
V2 = 6.0 L

Use P1V1 = P2V2, where P2 = (P1*V1)/(V2) = (9.00atm*2.00L)/(6.0 L) = 3.0 atm??

delta P (change in P) = P2 - P1 = 3.0 atm - 9.00 atm = -6.0 atm?? (correct significant digits?)

2) A combustion cylinder (containing a fixed number of moles of gas initially with a pressure of 4.00atm ) with a fixed piston changes temperature from 9.00 kelvin to 4.00 kelvin. Determine the change in pressure during this action.

P1 = 4.00 atm
T1 = 9.00 K
P2 = ?
T2 = 4.00 K

Use P1/T1 = P2/T2, where P2 = (P1*T2)/(T1) = (4.00 atm)(4.00 K)/(9. 00K) = 1.7778 atm??

Change in pressure (delta P) = P2 - P1 = 1.78 atm - 4.00 atm = -2.22 atm???

Thank you for any help.
 
381
2
i think it is ok as i don't see any mistakes.
 

lightgrav

Homework Helper
1,248
30
The only thing to worry about is whether your gas CONDENSES as it cools to 4 Kelvin. At such low Temperatures, almost nothing acts like an IDEAL gas.
 
Well, exactly what formula/method would you use if it wasn't an ideal gas?
 

Pengwuino

Gold Member
4,854
14
Well if he was not given any more information, you must assume it uses the ideal gas law... you would need experimental values otherwise i believe.
 

kp

53
0
use the Van Der Waals equation for real gases.
 

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