Science Help - temperature, pressure etc,?

Question

One hundred cubic meters of gas at -34.6°C and 200 kPa absolute pressure is compressed to a volume

of 25 cubic meters and an absolute pressure of 1000 kPa. What is the new temperature, in degrees

Celsius?

A. 2.5°C

B. 25°C

C. 5°C

D. 298°C

how did you get this? ???

Answer 1

P1V1/T1 = P2V2/T2 (Change C to K to lose negative)

(200kPa)(100cmt)/(238.55K) = (1000kPa)(25cmt)/(T2)

5963750 = 20000T2

298.19K -273.15 = 25C ( answer B)

The trick is to convert to Kelvin so that the negative is not on only one side of the equation, then, it is a simple equality with a formula to work.

Answer 2

Use the ideal gas law. PV= nRT

Using algebra, PV/nRT (using your beginning values) = PV/nRT (using your final values).

You can cancel out n and R, because they're the same for both sides of the equation.

Then you get PV/T (before) = PV/T (after)

20,000/(273-34.6) = 25,000/T

So, T= 25,000 (238)/20,000 = 298 K (this is in KELVINS)

Then convert to Celsius by subtracting 273.