1. A sample of methane gas has a volume of 38mL at a pressure of 2.2atm. What is
ID: 590636 • Letter: 1
Question
1. A sample of methane gas has a volume of 38mL at a pressure of 2.2atm. What is the volume of the gas (in mL) at 6.1 atm? Assume that there is no change in the temperature and the amount of the gas.
2. A weather balloon has a volume of 3.01 L when filled with helium at 30.9 oC at a pressure of 629.6 torr. What is the new volume of the ballon (in liters) if the balloon rises to a point where the air pressure is 382.9 torr and the temperature is -13.81 oC?
3. The half-life of 14O is 71 seconds. If you start with a 117 milligram sample of 14O, how much of your sample is left after 284 seconds?
4.
Explanation / Answer
Q1
Apply:
P1V1 = P2V2
2.2*38 = 6.1*V2
V2 = 2.2*38/6.1 = 13.704 Liters
Q2
similarly:
P1V1/T1 = P2V2/T2
629.6*3.01/(30.9+273.15) = 382.9*V/(-13.81+273.15)
V = 629.6*3.01/(30.9+273.15) /382.9 * (-13.81+273.15)
V = 4.2215Liter
Q3
Apply half life:
A = A0*(1/2)^(t(HL)
A = 117*(0.5)^(284/71)
A = 7.31 mg of O14 is left
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