Posted by Anonymous on .
A sample of argon at 300. °C and 50.0 atm pressure is cooled in the same container to a temperature of 0. °C. What is the new pressure?
105 atm
45.5 atm
54.9 atm
23.8 atm
42.7 atm

chem. 
Dr Russ,
First use school boy logic to dismiss any silly answers. If the temperature has dropped then the new pressure must be less than 50.0 atm. Thus we can dismiss 105 atm, and 54.9 atm.
Use P1/T1=P2/T2
or by inspection the temperature has dropped by approximately a factor of 2 (from 573 K to 273 K) so the pressure is approximately half the starting pressure of 50 atm. Thus the answer must 23.8 atm.
[and no calculator needed!]