Dalton’s law predicts the concentration of mixed gases in terms of pressure. It states that the sum of the pressure exerted by the entire gas mixture is equal to the sum of all pressures in the mixture. It applies to ideal gases as an absolute empirical law and has real-life applications.
Dalton’s law is a principle used in chemistry to predict the concentration of mixed gases in terms of pressure. Also known as Dalton’s law of partial pressure, it states that the sum of the pressure exerted by the entire gas mixture is equal to the sum of all pressures in the mixture. Introduced in the early 1800s by John Dalton, an English chemist and physicist, Dalton’s law applies to ideal gases as an absolute empirical law and not to real gases. The reason for this is due to the elastic properties of the molecules involved in the former, as well as the low particle volume. However, the margin of error applied to real gases is generally considered to be minimal in most cases.
Mathematically, Dalton’s law can be expressed as P(1) + P(2) + …P(n), where P = Pressure. As the law observes, the combined pressure of each gas component in the mixture is equal to the total pressure of each gas in the entire mixture. The measurement to represent pressure is expressed in kilopascal units and written as kPa.
Almost everyone has observed this phenomenon firsthand at some point, whether or not they are familiar with Dalton’s Law. One might also recall the classic science experiment from their school years which involved moving water from a glass bottle while being held under a water filled trough. The lesson learned was that although the bottle had been emptied of water, it hadn’t actually been left empty. Instead, it filled with invisible gas as the water was displaced. This same effect can be observed when doing something as mundane as washing a glass in a kitchen sink full of water or watching a child play with a plastic cup in the bathtub.
In the above scenario, it is possible to determine the amount of pressure exerted by the invisible gas captured in the bottle, namely hydrogen. This is done by referring to a table showing water vapor pressure at varying temperatures, since a certain amount of water vapor must be factored into the equation. The calculation would be the total amount of pressure minus the water vapor pressure. The result would be equal to the pressure of the hydrogen gas.
While Dalton’s Law primarily serves a purpose in the laboratory, it also has real-life applications. For example, divers are concerned with knowing how air and nitrogen are affected at different pressures at different water depths. It is also used to determine the concentration of specific gases in the atmosphere.
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