Question

The diameter of an approximately spherical May Day ball is 35 cm. The balloon is filled with helium so that the balloon has an overpressure of 0.12 bar at a temperature of 18°C. What is the mass of helium in the sphere?

Answer 1

$$pV=\frac{m}{M}RT\to \frac{4}{3}\pi r^3p=\frac{m}{M}RT$$

$$\frac{4}{3}\pi (0.35)^3(0.12\cdot 10^5)=\frac{m}{4}(8.31)(273+18)$$

$$m=3.6\ g$$