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Which Is Correct about Henry’s Law

Henry`s Law is a limiting law that applies only to “sufficiently diluted” solutions, while Raoul`s Law is generally valid when the liquid phase is almost pure or for mixtures of similar substances. [13] The concentration range in which Henry`s Law applies narrows the further the system deviates from ideal behavior. Basically, it`s chemically “different” from the solvent solute. The reason for choosing a standard state of Henry`s law can be seen in Figure 6.13, which compares the standard states of Henry`s law and Raoult`s law for CCl4 in {x1(C4H9)2O + x2CCl4}. At high x2, the behavior of Raoult`s law for CCl4 is approximated and the default state of a Raoult distribution allows a2 to be represented by x2. On the other hand, Henry`s law is a better approximation to low x2 (or m), and a standard state of Henry`s law allows a2 to be represented by x2 (or m).x The solubility of permanent gases generally decreases with increasing temperature to about room temperature. For aqueous solutions, however, the solubility constant of Henry`s law passes through a minimum for many species. For most permanent gases, the minimum is below 120°C. The smaller the gas molecule (and the lower the solubility in water), the lower the temperature of Henry`s Law maximum constant. The maximum is about 30 °C for helium, 92 to 93 °C for argon, nitrogen and oxygen, and 114 °C for xenon. [10] When the cylinder is opened, pressurized CO2 escapes into the atmosphere (usually accompanied by a hissing sound).

As the partial pressure of CO2 in the atmosphere above the beverage decreases rapidly, the solubility of carbon dioxide in the beverage also decreases (due to Henry`s Law). As a result, the dissolved CO2 reaches the surface of the beverage in the form of tiny bubbles and escapes into the atmosphere. An example where Henry`s Law comes into play is the depth-dependent dissolution of oxygen and nitrogen in the blood of scuba divers, which changes during decompression and leads to decompression sickness. A daily example is the experiment with soft drinks that contain dissolved carbon dioxide. Before opening, the gas above the beverage in its container is almost pure carbon dioxide, at a pressure higher than atmospheric pressure. After opening the cylinder, this gas escapes and shifts the partial pressure of carbon dioxide onto the liquid much lower, resulting in degassing as dissolved carbon dioxide escapes from the solution. The values of Henry`s Law constants for aqueous solutions depend on the composition of the solution, i.e. its ionic strength and dissolved organic compounds. In general, the solubility of a gas decreases with increasing salinity (“salting”). However, a “salt effect” has also been observed, for example for Henry`s effective law constant of glyoxal. The effect can be described using Sechenov`s equation, named after the Russian physiologist Ivan Sechenov (sometimes the German transliteration “Sechenov” of the Cyrillic name Се́ченов is used).

There are many alternative ways to define the Setchenov equation, depending on how the composition of the aqueous phase is described (based on concentration, molality, or molar part) and which variant of Henry`s Law constant is used. The description of the solution in terms of molality is preferable because the molality is invariant to temperature and the addition of dry salt to the solution. Thus, Sechenov`s equation can be written as follows: There are many ways to define the proportionality constant of Henry`s law, which can be divided into two basic types: One possibility is to put the aqueous phase in the numerator and the gas phase in the denominator (“aq/gas”). This results in the Henry H solubility constant s {displaystyle H_{rm {s}}}. Its value increases with increasing solubility. Alternatively, the numerator and denominator can be switched (“gas/aq”), resulting in the Henry volatility constant H v {displaystyle H_{rm {v}}}. The value of H v {displaystyle H_{rm {v}}} decreases with increasing solubility. IUPAC describes several variants of the two basic types. [3] This is due to the multitude of sizes that can be chosen to describe the composition of the two phases. Typical options for the aqueous phase are molar concentration (c a {displaystyle c_{rm {a}}}), molality (b {displaystyle b}) and molar mixing ratio (x {displaystyle x}).

For the gas phase, molar concentration ( c g {displaystyle c_{rm {g}}} ) and partial pressure ( p {displaystyle p} ) are often used. It is not possible to use the gas phase mixing ratio (y {displaystyle y} ) because for a given gas phase mixing ratio, the aqueous phase concentration c a {displaystyle c_{rm {a}}} depends on the total pressure and therefore the ratio y / c a {displaystyle y/c_{rm {a}}} is not a constant. [4] To specify the exact variant of Henry`s law constant, two superscript characters are used. They refer to the numerator and denominator of the definition. For example, H s c p {displaystyle H_{rm {s}}^{cp}} refers to Henry`s solubility defined as c/p {displaystyle c/p}. Since ozone oxidation is important at higher pH values, this reaction is particularly important for sea salt particles from seawater that have a pH of ∼8. Thus, SO2 can be absorbed as sea salt particles and oxidized by ozone to sulphate. Due to the presence of buffering agents such as carbonates in the particulate matter, this oxidation continues until the buffering agents are exhausted, after which the pH decreases and the rate of ozone oxidation decreases; As briefly discussed, reactive chlorine and bromine species may also be involved in the oxidation of S(IV) in sea salt particles (see, for example, Clarke and Radojevic, 1983; Clarke and Williams, 1983; Miller et al.