Question

1. A gas that has a volume of 28 L, a temperature of 45 °C, and an unknown pressure has its volume increased to 34 L and its temperature decreased to 35 °C. If the pressure is measured after the change to be 2.0 atm, what was the original pressure of the gas?

a. 4.1 atm
b. 3.2 atm
c. 2.5 atm
d. 1.6 atm

2. An unknown volume of gas has a pressure of 0.50 atm and temperature of 325 K. If the pressure is raised to 1.2 atm and the temperature decreased to 320 K, giving a new volume of 48 L, what was the initial volume?
a. 140 L
b. 65 L
c. 87 L
d. 120 L

Answer 1

1.) C
V1=28L, T1=318K, P1=?, V2=34L, T2=307K, P2=2 atm
PV=nRT
(2)(34)=(n)(.08201)(307)
(68)=(n)(25.17707)
n=2.70087 mol
(P1)(28)=(2.70087)(.0821)(318)
(P1)(28)=(70.51378)
P1=2.518349 atm
2.) D
V1=?, P1=0.50 atm, T1=325K, P2=1.2 atm, V2=48L, T2=320K
PV=nRT
(1.2)(48)=(n)(.0821)(320)
(57.6)=(n)(26.272)
n=2.192448 moles
(0.50)(V)=(2.192448)(0.0821)(325)
(0.50)(V)=(58.5)
V=117 L