The mass of a gas dissolved in a liquid is proportional to the pressure of the gas above the surface of the liquid.

Henry’s Law describes the process of dissolving a gas in a liquid. What is the liquid in which the gas is dissolved, we know from the example of carbonated drinks – non-alcoholic, low-alcohol, and on big holidays – champagne. All these drinks have dissolved carbon dioxide (chemical formula CO2) Is a harmless gas used in the food industry due to its good solubility in water, and all these drinks foam after opening a bottle or can for the reason that the dissolved gas begins to escape from the liquid into the atmosphere, since after opening a sealed vessel, the pressure inside drops.

Actually, Henry’s law states a rather simple fact: the higher the gas pressure above the surface of the liquid, the more difficult it is for the gas dissolved in it to be released. And this is completely logical from the point of view of the molecular-kinetic theory, since a gas molecule, in order to break free from the surface of a liquid, needs to overcome the energy of collisions with gas molecules above the surface, and the higher the pressure and, as a consequence, the number of molecules in the boundary region, the it is more difficult for a dissolved molecule to overcome this barrier.

Henry’s Law also explains another property of fizzy drinks – the characteristic foam that tends to splash out after you open a bottle of soda or (if you’re lucky) champagne. In order to pump more gas into the drink, manufacturers deliberately clog bottles and cans under high surface pressure, and in champagne it is completely injected by itself in the process. fermentation and natural emission of carbon dioxide inside the bottle.

When you tug on the ring of a can or open a bottle, the high-pressure carbon dioxide inside produces a characteristic pop or hiss. The pressure above the surface of the liquid drops rapidly, equalizing with atmospheric pressure, and the CO molecules2 begin to stand out freely from the drink in which they were dissolved, as a result of which the drink bubbles and foams. Sooner or later, the dissolved carbon dioxide will be released from the liquid, almost all, the pressure of the CO dissolved in the liquid directed to the surface2 will be equal to atmospheric, and the drink will stop foaming and bubbling. That’s why fizzy drinks when uncorked fizzle out – and quickly enough.

It turns out that physical meaning can even be found in a can of soda.

William HENRY
William HENRY
William Henry, 1774-1836

English chemist and physicist. Born into the family of the owner of a chemical manufactory in Manchester. He studied at the Faculty of Medicine at the University of Edinburgh, after graduating from it, worked in a morgue in Manchester. Having inherited the family chemical manufactory, he devoted his free time to physical and chemical research. Besides the law that bears his name, Henry discovered the chemical formula of ammonia and discovered the difference between methane and ethylene. In addition to research (on which he spent a significant part of the family inheritance) Henry left behind the textbook “Elements of Experimental Chemistry” (Elements of Experimental Chemistry), recognized as the most successful textbook on chemistry of the first half of the 19th century. A close friend and collaborator of Henry was another prominent scientist of the time, John Dalton (cm. Dalton’s Law), and the son of William Henry Sr., William Charles Henry, subsequently wrote the first and most complete biography of a friend of his father.

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