1. You may have seen a Fizz-Keeper sold in supermarkets. It's a plastic
attachment you screw onto a plastic soda bottle. You pump it to force air
into the bottle. This creates a higher air pressure above the soda, so it
should preserve the soda from going flat. Makes sense. However, my
chemistry colleague recently informed me that this does not work! He said
the partial pressure of CO2 will be the same whether you increase the air
pressure or simply put the cap on. The best way to preserve the fizz would
be to add CO2 gas, or simply squeeze the bottle to remove most of the air
and then cap it. Does this make sense? I know physics, but not as much
chemistry.
2. If you shake a plastic bottle of unopened soda, the inside pressure
should remain the same since it is a closed system. But if you then
squeeze the bottle, it certainly feels like the pressure has increased. Is
this a temporary thing until equilibrium is established after some time?