A balloon filled with helium
Question:

A balloon filled with helium $\left(32^{\circ} \mathrm{C}\right.$ and $\left.1.7 \mathrm{~atm} .\right)$ bursts. Immediately afterwards the expansion of helium can be considered as :

1. irreversible isothermal

process $\Delta Q=0$, so adiabatic.