Tuesday, 30 April 2013

Solubility of Gases

As the temperature of a liquid increases, the solubility of gases in that liquid decrease. We can use the Second Law of Thermodynamics to explain why. Heating a solution of a gas enables the particles of gas to move more freely between the solution and the gas phase. The Second Law predicts that they will shift to the more disordered, more highly dispersed, and therefore, more probably gas state.
In a similar way, we can explain why the substances that are solids at room temperature and pressure tend to become more soluble when the temperature rises. Heating a solution of a solid makes it easier for the particles of solid to move between the solution and the solid phase. The Second Law predicts that they will shift to the more disordered, more highly dispersed, and therefore, more probably solution state
The second law of thermodynamics: in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state.
In the case of an exothermic reaction, because energy is entering the system, the potential energy of the state is more than that of the initial state.
Because of this, the particles in the gas are more energised in the warmer solution and thus spread out more, leading to a lesser solubility of the gas in water.
Along with this, Charles’ law states: For a fixed quantity of gas at a given temperature, the volume increases linearly with temperature.
Thus the solubility of a gas decreases as the temperature increases because the volume of the gas increases as temperature increases.


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