We can use the ideal gas law to calculate the volume of the balloon at 240 degrees Celsius. The ideal gas law states that PV = nRT, where P is the pressure, V is the volume, n is the number of moles of gas, R is the ideal gas constant, and T is the temperature.

We know the pressure (1 atm), the temperature (240 degrees Celsius or 513 Kelvin), and the number of moles of gas (let's assume it is 1 mole). The ideal gas constant is 0.08206 L * atm / mol * K.

Plugging these values into the ideal gas law, we get:

1 atm * V = 1 mole * 0.08206 L * atm / mol * K * 513 K

Solving for V, we get:

V = 42.56 L

Therefore, the volume of the balloon at 240 degrees Celsius is 42.56 L.