ChemistrySeminar, Solubility of gases in liquids, Henry's law and it's applications

Solubility of gases in liquids
Henry's Law and it's applications

1. CHEMISTRY
SEMINAR
Subject Code : ED1105
Subject Name : Thermodynamics,Equilibrium,and Solutions
NIT PUDUCHERRY
Department of Education

2. Solutions of gases in liquids
Henry’s Law and its application

3. Solution of gases in
liquids
⚬Asolutionisauniform(homogeneous)mixtureoftwoormore
substances.
Example:Saltwater→Salt+Water
⚬Thesoluteisthesubstancethatgetsdissolvedinanother
substance.
Itisusuallypresentinasmalleramount.
Example:Insaltwater,saltisthesolute.
⚬Thesolventisthesubstancethatdissolvesthesolute.
Itisusuallypresentinalargeramount.
Example:Insaltwater,wateristhesolvent.

4. When a gas dissolves in a liquid, the result is
known as gas-liquid solution.
Eg: Carbonated drinks(CO2 dissolved in water)
Solubility of gases in liquid refers to the
maximum amount of gas that can dissolve in a
given amount of liquid at a given temperature

5. Factors affecting solubility of
gases in liquids
1.Nature of solute and solvent
Polar gases dissolves better in polar solvents and non polar
dissolves in non polar solvents.
Eg:Ammonia (NH3) gas can interact strongly interact with polar
solvent water(H2O).
NH3 + H2O ---> NH4OH
Oxygen(O2) is sparingly soluble in water
2.Temperature
Gas solubility decreases with an increase in temperature. Higher
temperature give gas molecules more kinetic energy making them
escape more easily from the liquid.
3.Pressure
Solubility of gas in liquid increases with increasing pressure.

6. Henry’s Law
“The amount of gas that is dissolved in a
liquid is directly proportional at equilibrium to
its partial pressure above the liquid”
P=kH ×x
⚬P = partial pressure of the gas above the liquid
⚬x = mole fraction (solubility) of the gas in the liquid
⚬kₕ (Henry’s constant) = proportionality constant (depends
on gas and temperature)

7. Applications of Henry’s Law
1.Soft drinks and soda bottles:
In soft drinks, carbon dioxide gas is dissolved under high pressure. When the bottle
is opened, the pressure decreases, and carbon dioxide escapes from the liquid,
making the drink lose its fizz. This principle is used to keep the drink carbonated.
2.Scuba diving:
During deep-sea diving, gases such as nitrogen and oxygen dissolve in a diver’s
blood under high pressure. If the diver rises to the surface too quickly, the pressure
suddenly decreases, and these gases form bubbles in the blood, causing a painful
condition known as bends or decompression sickness. To prevent this, divers use a
special mixture of gases.
3.Mountaineers and high-altitude breathing:
At high altitudes, the air pressure is low, so less oxygen dissolves in the blood. This
leads to breathing difficulties or mountain sickness. To overcome this problem,
mountaineers carry oxygen cylinders.

8. Questions
Q.TheHenry'slawconstantKHforCO2inwaterat298Kis1.97x10^8Pa.
CalculatetheamountofCO2in1literofsodawaterwhenpackedunder2.5atm
CO2pressureat298K.

9. Questions
Q.TheHenry'slawconstantforoxygeninH2Oat298Kis1.3x105atm.The
partialpressureofgasoxygenintheatmosphereisapproximately0.21atm.
CalculatethesolubilityofoxygeninH2Oat298Kundertheseconditions.

10. 3)Asoftdrinkbottleisopenedatroomtemperature.Aftersometime,itgoesflat.Whatwould
happenifthesamebottlewaskeptinarefrigeratorandthenopened?
a)Itwouldgoflatfaster.
b)Itwouldfizzlessinitiallybutgoflatatthesamerate.
c)Itwouldfizzmoreinitiallyandtakelongertogoflat.
d)Itwouldfizzlessinitiallyandtakelongertogoflat.
Questions
Explanation:
Henry’sconstant(Kh)increaseswithtemperature.Thismeansgasesdissolvelessinliquidsat
highertemperature.AtlowertemperatureKhissmaller,sogasesaremoresoluble.Whenyou
openachilledsoftdrinkthegasabovetheliquidescapesmoreslowlybecausethecoldliquid
holdsmoreCO2soitfizzeslessatfirstandstaysfizzylonger.

11. Questions
4) Four different gases W, X, Y, Z are bubbled through water at the same temperature and
partial pressure. The Henry's law constant \(K_{H}\) for these gases are given below. Which gas
is most soluble in water?
Explanation:
Henry's law is expressed as P=Kh×X or X=P/Kh.This shows that the solubility(X) is
inversely proportional to Henry's constant(Kh). A lower Henry's constant for a given partial
pressure means higher solubility.

12. Questions
5) Which of the following conditions is most favorable for increasing the solubility of a gas in a
liquid?
a) High temperature, high pressure
b) High temperature, low pressure
c) Low temperature, high pressure
d) Low temperature, low pressure
High Pressure increases the partial pressure of the gas above the liquid, forcing more gas
molecules into the solution (Henry's Law).Low temperature decrease kinetic energy of the gas
molecules, making it easier for them to be trapped and dissolved in the liquid.
Explanation:

13. Thank
You
Presented by
Ann Merin K.S
ED24B1009