Explain the equilibrium in soda water and explain it using Henry's law.

(N/A) In a closed soda water bottle,a saturated solution of $CO_{2}$ gas is maintained under high pressure. An equilibrium exists between the $CO_{2}$ molecules dissolved in water and those in the gaseous state:
$CO_{2(g)} \rightleftharpoons CO_{2(aq)}$ ... $(I)$
(At constant pressure and temperature)
Henry's law states that the mass of a gas dissolved in a given volume of a solvent at a constant temperature is directly proportional to the partial pressure of the gas present above the surface of the solution.
Mathematically,$m \propto p$ or $p = K_{H} \cdot x$,where $p$ is the partial pressure of the gas,$x$ is the mole fraction of the gas in the solution,and $K_{H}$ is Henry's law constant.
As the pressure of $CO_{2}$ above the liquid is high in a sealed bottle,the solubility of $CO_{2}$ in water is high. When the bottle is opened,the pressure of $CO_{2}$ above the liquid drops to the atmospheric pressure. According to Henry's law,the solubility of the gas decreases as the pressure decreases. Consequently,the excess dissolved $CO_{2}$ escapes from the solution to reach a new equilibrium,causing the soda water to become 'flat'.