This law states that at constant temperature the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid surface. If S is the solubility of the gas then:
Here S is the solubility of the gas in mol/litre
P is the partial pressure of the gas in atm.
Here KH is Henry’s constant.
It depends upon nature of gas, nature of liquid and temperature.
Q: - What is the necessary condition for Henry’s law?
Ans: - Non-reactivity of gas and liquid.
APPLICATIONS OF HENRY LAW
(1)CO2 is filled in the soft drinks and soda water under high pressure to increase its solubility(2) In order to overcome the problem of bends in sea divers the oxygen in the cylinders is mixed with helium as it causes less discomfort than nitrogen in the scuba divers.
(3)Due
to low concentration of oxygen at higher altitudes people lose power of clear
thinking and become weak .This condition of the body is known as anoxia.
NUMERICALS ON HENRY’ S LAW
Q :- The solubility of nitrogen gas in water at 25 and 0.78 atm pressure is 5.3*10-4 M. Calculate Henry’s constant for nitrogen in water. Ans :- 6.79*10-4 M/atm.
Q :- The Henry’s law constant for He gas in water at 30 is 3.7*10-4 M/atm at 2.5 atm pressure . Calculate solubility of He gas. Ans :- 9.25*10-4 M
Q :- What pressure of CO2 is required to keep the solubility of CO2 0.12 M in soda bottle at 25 .Given Henry’s constant for CO2 =3.14*10-2 M/atm. Ans :-3.85 atm
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