Question

1. A helium-filled balloon had a volume of 8.50 L on the ground at 20.0°C and a

pressure of 750.0 Torr. After the balloon was released, it rose to an altitude where the
temperature was 40.0°C and the pressure was .550 atm. What is the new volume of
the balloon in liters at the high altitude?

Answer 1

133.74 L

Step-by-step explanation:

First we convert the given pressures and temperatures into atm and K, respectively:

• 750.0 Torr ⇒ 750/760 = 0.9868 atm

• 20°C ⇒ 20+273.16 = 293.16 K

• 40°C ⇒ 40+273.16 = 313.16 K

Then we use the PV=nRT formula to calculate the number of moles of helium in the balloon, using the data of when it was on the ground:

• 0.9868 atm * 8.50 L = n * 0.082 atm·L·mol⁻¹·K⁻¹ * 293.16 K

• n = 2.866 mol

Then, knowing the value of n, we use PV=nRT once again, this time to calculate V using the data of when the balloon was high up:

• 0.550 atm * V = 2.866 mol * 0.082 atm·L·mol⁻¹·K⁻¹ * 313.16 K

• V = 133.74 L