Henry’s Law

            It states that the solubility of a gas at a given temperature is directly proportional to the pressure at which it is dissolved.

Or        

             

          Where p = Partial pressure of the gas

            = Mole fraction of the gas

            = Henry law constant

(1)        Significance of Henry law constant:-

            (a)        The unit of Henry law constant is some as those of pressure i.e. torr or k bar.

            (b)        Different gases have different values of Henry law constant.

            (c)        The KH values of a gas increases with the increase in temperature.

            (d)       The solubility of a gas can be calculated at a given temperature if its KH value is                                   known. In general, a gas having lower value of KH has higher solubility.   

(2)        Limitations of Henry’s law:-

            (a)        The pressure of the gas is not too high.

            (b)        The temperature is not too low.

            (c)        The gas should not undergo any chemical reaction with the solvent.

            (d)       The gas should not undergo dissociation in solution.

(3)        Applications of Henry’s law:-

            (a)        Soft drinks, soda water and other carbonated beverages contain dissolved carbon                     dioxide.

            (b)        In lungs oxygen present in the inhaled air dissolves in blood because of its high                                     partial             pressure and combines with hemoglobin to form oxohaemoglobin.

            (c)        The minimize the painful effects accompanying the decompression of deep sea                          divers,             oxygen is diluted with less soluble helium gas in the breathing kit.