Answer:
Here's what I find
Explanation:
The aqueous acid causes the iron to react with the oxygen in the air.
The reaction is probably
2Fe + O₂ + 4H⁺ ⟶ 2Fe²⁺ + 2H₂O
The removal of oxygen causes the pressure inside the bottle to decrease.
The greater outside pressure causes the balloon to inflate into the bottle in an inverted manner.