Opening a Soda on the Ocean Floor

Chris Hadfield is among the best of us.

He's a fickin' astronaut, a pretty nifty quitar player, a hell of a pilot, a great science communicator, the father of an interesting YouTuber, and a good sport.

In this video, Chris doesn't do a lick of science explaining, but he does demonstrate the fact that if you're going to shake up a soda can and immediately open it, you'd best be under double atmospheric pressure at the bottom of the ocean.

To fill in what Chris doesn't explain, the fizzing is largely a result of this equilibrium...

H₂CO_{3 (aq)}  ⇌   H₂O _(l) + CO_{2 (g)}

At normal atmospheric pressure that CO₂ pressure is low, so the reaction shifts to the right until it reaches equilibrium and your pop is flat. Allowing the pressure to build up in a sealed container - keeping the coke bottle closed up - stops this from progressing because eventually Q = K. So does cooling down the tonic container because the reaction is exothermic and endothermic reactions (the reverse reaction, keeping the gas dissolved in the solution as carbonic acid) are favored at colder temperatures.

But at the bottom of the ocean, there's apparently a high enough CO₂ pressure in the atmosphere that the soda doesn't immediately fizz up.