Aspherical balloon of volume 4.12 103 cm3 contains helium at a pressure of 1.24 105 pa. how many moles of helium are in the balloon if the average kinetic energy of the helium atoms is 3.60 10-22 j? part 1 of 4 - conceptualize the balloon has a volume of 4.12 l and a diameter of about 20 cm, which seems like a reasonable size for a large toy balloon. the pressure of the balloon is only slightly more than 1 atm, and if the temperature is close to room temperature, we can use the estimate of 22 l/mol for an ideal gas at stp conditions. if this is valid, the balloon should contain about 0.2 moles of helium