chemistry
posted by Please Help! .
i keep trying to do these problems and i don't understand them. please help me!!
1. Gas stored in a tank at 273 K has a pressure of 388 kPa. The save limit for the pressure is 825 kPa. At what temperature will the gas reach this pressure?
A. 850 K
B. 925 K
C. 580 K
D. 273 K
2. At 10 degrees C, the gas in a cylinder has a volume of 0.250 L. The gas is allowed to expand to 0.285 L. What must the final temperature be fore the pressure to remain constant? (Hint: Convert from degrees Celsius to kelvins using the expression C +273 = K)
A. 273 K
B.283 K
C. 323 K
D. 383 K
3.A gas has a volume of 5.0 L at a pressure of 50 kPa. What is the volume when the pressure is increased to 125 kPa? The temperature does not change.
A. 5.0 L
B. 3.0 L
C. 4.0 L
D. 2.0 L

All of these problems can be solved with the perfect gas law relationship
P V/T = constant
For example, in #3, T is constant so P*V = constant. Therefore
P1*V1 = P2*V2, where
"1" and "2" refer to initial and final conditions.
50 kPA*5.0 L = 125 kPa * P2
P2 = (50/125)*5.0 = 2.0 L (answer D)
Try doing the others yourself to get familiar with this type of problem 
3. A

#3 is D because the pressure is increased 2.5 times. So, you would divide 5.0 by 2.5 to get 2.0 L.