A balloon filled with helium (32ᵒC and 1.7 atm.) bursts. Immediately afterwards the expansion of helium can be considered as

Solution

Physics sir · 4 steps

A burst is sudden: no time for heat to flow, and no slow steps. So it is irreversible and adiabatic.

1. Too fast for heat. The helium rushes out in a fraction of a second. Heat exchange with the surroundings needs time, so almost no heat flows in or out: Q ≈ 0. That makes the process adiabatic.
2. Not reversible. A reversible process is very slow, with the gas pressure always just balancing the outside pressure. Here the gas at 1.7 atm suddenly meets air at about 1 atm and expands violently, with turbulence. It never passes through equilibrium states, so it is irreversible.
3. Not isothermal. An isothermal process needs steady heat exchange to hold the temperature fixed. In a sudden burst there is no time for that, so the temperature cannot stay at 32°C.
4. So. The expansion is sudden (adiabatic) and uncontrolled (irreversible), so the answer is (a), irreversible adiabatic.

The idea to keep. Sudden processes like bursting, puncturing or a quick compression are adiabatic, because heat has no time to flow. They are also irreversible, because the gas is never in equilibrium.

Answer from the NTA final answer key. Solution by PrepWiser.