What is Dalton's Law?

Describes the characteristics of an ideal gas. This rule of thumb was observed by John Dalton in 1801. In a gas mixture in any container, if no chemical reaction occurs between the components, each gas is evenly distributed throughout the container, the pressure it generates and the pressure it generates when it occupies the entire container alone the same.

Chinese name: Dalton's law of partial pressure
Foreign name: Daltons law of partial pressures
discoverer: Dalton

Application area: physical
Application range: physical
nickname: Dalton's Law

Basic information on Dalton's partial pressure law

Introduction to Dalton's law of partial pressure

Dalton's partial pressure law (also known as Dalton's law ) describes the properties of an ideal gas. This rule of thumb was observed by John Dalton in 1801. In a gas mixture in any container, if no chemical reaction occurs between the components, each gas is evenly distributed throughout the container, the pressure it generates and the pressure it generates when it occupies the entire container alone the same. That is, the pressure of a certain amount of gas in a certain volume of container is only related to temperature. For example, at zero degrees Celsius, the pressure of 1mol oxygen in a volume of 22.4L is 101.3kPa. If 1 mol of nitrogen is added to the container and the volume of the container is maintained, the pressure of oxygen is still 101.3 kPa, but the total pressure in the container is doubled. It can be seen that the pressure generated by 1 mol of nitrogen in this state is also 101.3 kPa. Dalton's partial pressure law is only applicable to ideal gas mixtures in principle, but it can also be approximately applied to real gas mixtures at low pressures.

Dalton summarized these experimental facts and reached the following conclusions: the partial pressure generated by a gas in a gas mixture is equal to the pressure generated when it alone occupied the entire container at the same temperature; and the total pressure of the gas mixture It is equal to the sum of the partial pressures of the gases. This is the law of partial pressure.

That is, the partial pressure of a component B in an ideal gas mixture is equal to the pressure that the component has under the conditions of the temperature T and the total volume V of the mixed gas alone. The total pressure of the mixed gas is equal to the sum of the pressures generated by the individual components in the temperature and volume of the mixed gas. This is Dalton's law of partial pressure.

Dalton's law applies only to ideal gas mixtures. Actual gases do not strictly follow Dalton's partial pressure law, especially under high pressure. When the pressure is high, the volume occupied by the molecules and the space between the molecules are comparable; at the same time, the shorter intermolecular distance increases the intermolecular force, which will change the partial pressure of each component. These two points are not reflected in Dalton's law.

Dalton's Partial Pressure Law History

Dalton was born in Eagle Farm, Northern England in 1766. He had only received formal education before the age of 11, and had almost completely mastered scientific knowledge by himself. He was precocious and became a teacher at the age of 12. He moved to Kendall at the age of 15 and moved to Manchester at the age of 26, living there until his death in 1844. He never married.

Dalton became interested in meteorology in 1787 and six years later published a book on meteorology. The study of air and the atmosphere made him interested in the characteristics of general gases. Through a series of experiments, he discovered two important laws concerning the properties of gases. The first law was proposed by Dalton in 1801, which believed that the volume occupied by a gas is proportional to its temperature (commonly known as Charles's law, named after French scientist Charles. I discovered this law a few years ago, but failed to publish its results). The second law was proposed in 1801 and is called Dalton's law of partial pressure of gas.

In 1804 Dalton proposed his atomic theory systematically and compiled an atomic weight table. But his main book, The New System of Chemical Philosophy, was not published until 1808, and it was his success. He received many honors in his later years.

Incidentally, Dalton suffers from color blindness. The symptoms of the disease aroused his curiosity. He began to study this subject, and eventually published a paper on color blindness-the first paper on color blindness ever published.

Achievements and Doctrines of Dalton's Partial Pressure Law

Dalton's Partial Pressure Law Character Achievement

British scientist John Dalton introduced the atomic hypothesis into the mainstream of science in the early 19th century. The key doctrines he provided have made tremendous progress in the field of chemistry since then.

Dalton's theory of partial pressure

To be precise, it was not Dalton who first proposed that all matter is composed of extremely tiny, indestructible particles, personal atoms. This concept was proposed by the ancient Greek philosopher De Mocrit, and may even have been proposed before him. Another Greek philosopher Epicurus (342-270 BC?) Adopted this hypothesis. The Roman writer Leuklithias (99? -55 BC) gave a vivid introduction to this hypothesis in his famous poem "On the Essence of Things".

Democritus's doctrine was not accepted by Aristotle, was ignored in the Middle Ages, and has no impact on modern science. But several leading scientists, including Isaac Newton, supported similar theories in the 17th century. However, early atomic theories were not expressed quantitatively or used in scientific research. Most fundamentally, no one saw the connection between the philosophical hypothesis and the harsh facts of chemistry.

This is where Dalton contributes. He came up with a clear quantitative doctrine that could be used to explain chemical experiments and withstood the exact tests of the laboratory.

Although Dalton's terminology is slightly different from what we use today, it clearly states the concepts of atoms, molecules, and elements. He made it clear that although the total number of atoms in the world is quite large, the number of different atomic species is very small. (His original work lists 20 elements, that is, 20 atoms. There are more than 100 elements known today. Species).

Although different kinds of atoms have different weights, Dalton believes that all properties, including weight, of any two atoms of the same type are the same. Dalton listed in his book a table of the relative weights of various types of atomsthe first table in this regard, which was an important feature of quantitative atomic theory.

Dalton also made it clear that two molecules of any identical compound are composed of the same atom (for example, each nitrous oxide is composed of two nitrogen atoms and one oxygen atom). It follows that a known compound-no matter how it is formulated or where it is found-always contains the same elements, and the weight ratio between these elements is exactly the same. This is the "law of ratio" discovered by Joseph Louis Prout in experiments a few years ago.

Dalton's doctrine is very convincing and has been adopted by most scientists in less than two decades. And chemists acted according to the scheme proposed in the book: accurately determine the relative atomic weight and number of atoms of each molecule; quantitatively analyze compounds. Of course this plan has achieved complete success.

The importance of the atomic hypothesis cannot be easily overstated. It is the main doctrine of our understanding of chemistry, and is to a large extent an indispensable prelude to modern physics. Just because Dalton had often discussed atomism before Dalton, his ranking in this volume was not high.