Final answer:
To extend the retention of carbonation in soft drinks, keep them chilled, reseal the container tightly after each use, minimize exposure to air, and store in a container with minimal headspace to maintain pressure.
Step-by-step explanation:
When a soft drink loses its carbonation, this is due to the loss of dissolved CO2 when the equilibrium is disrupted upon opening the bottle. To keep CO2 in solution the longest, you can minimize the escape of CO2 by keeping the soft drink chilled, resealing the container tightly after each pour, and minimizing the time the drink is exposed to the air. Additionally, storing the soft drink in a container with a small headspace can help maintain a higher pressure, slowing down the process of the soft drink becoming 'flat'.
The solubility of CO2 is directly related to the pressure applied to the liquid. By reducing the loss of pressure in the soft drink's headspace, you maintain a higher concentration of dissolved CO2. This is clearly observed when the soft drink is exposed to high concentrations of CO2 during the carbonation process, and the pressure above the liquid in the headspace increases as the CO2 begins to dissolve, until equilibrium is reached. When the container is then opened, you hear a hissing sound as this pressurized CO2 is released, and the equilibrium shifts. To counteract this, keep the soft drink as pressurized as possible and avoid pouring it into wide, open cups where more surface area is exposed.