a. How many moles of helium are in the balloon? (1 point)

n= (1.00 ) (3425 ) / (0.0821) (273 )
n= 152.8 moles of He
b. After the balloon is released, it begins to rise. At the altitude when its
pressure is 0.0474 atm and its temperature is 220.2 K, what is the volume of the
helium in the balloon? Assume that the force of the balloon on the gas is
negligible. (1 point)
V2 = [(1atm) (3425 L) (220.2 K)]/ [(0.0474 atm)(273 K)]
V2= 58,282.32 L He

c. Suppose another weather balloon is inflated with 8000 L of hydrogen.
Estimate its volume if it reaches the same elevation with this atmospheric
pressure and temperature. (1 point)
V2 = [(1atm) (8000L) (220.2 K)]/ [(0.0474 atm) (273 K)]
V2= 136,133.9L H
4. Two sealed tanks each contains gas at 273 K. Tank A contains 9.00 g of argon
gas, and tank B contains 18.7 g of chlorine gas.
a. How many moles of gas are in each tank? (2 points)
n
Ar
= 9/40 = 0.225 (mol)
n
Cl
= 18.7/(35,5) = 0.527(mol)

b. The volume of each tank is 5.00 L. Use the ideal gas equation to determine
the pressure of the gas in each tank. (2 points)
Pressure of argon = nRT/V = 0.225*0.082*273/5 = 1.007 atm
Pressure of chlorine gas = 0.527*0.082*273/5 = 2.359 atm
c. Explain why it is reasonable to treat the gases as ideal gases. Justify your
answer by explaining what the macroscopic properties of the gases imply about
the intermolecular forces within the gases. (1 point)
Since the pressure is low and the temperature of the gases is much higher than
their boiling points, it is reasonable to assume that the gases behave ideally.

d. Suppose a researcher wants to increase the non-ideal behavior of the gases.
Should the researcher increase the temperature to
T
= 925 K, or should the
researcher decrease the temperature to
T
= 92.5 K? Explain why each of these
possibilities would or would not affect the non-ideal behavior of the gases. (1
point)