Dalton’s Law: History, Definition, along with the problems and discussion

Dalton’s Law: History, Definition, along with the Problems and Discussion –   Dalton’s Law is one of the branches of chemistry, the study of the elements found in living and non-living things. Laws that are useful to complement existing parts of the theory are Proust’s law of fixed proportions and Lavoisier’s law of conservation of mass.

The law of fixed proportions or Proust’s law says that a compound is a combination of two elements, where the mass ratio of the elements will always be the same. For example CO and CO2 compounds. The mass ratio of both C and O is 1:2.

Meanwhile, the law of conservation of mass or Lavoiser’s law says that the ratio between the masses of substances before and after the reaction is the same. Even though the compound decomposes, it does not disappear but forms new compounds that are likely to bond with other elements.


Dalton’s Law is the third basic law of chemistry after Proust’s Law and Lavoiser’s Law which will be discussed specifically in the following article. Previously, let’s first get to know John Dalton as the discoverer of Dalton’s Law.

John Dalton was a physicist as well as a meteorologist who was born on September 6, 1766 in Eaglesfield, Cumberland, England and died on July 27, 1844 in Manchester, Lancashire, England.

Dalton was not born into a family that has a high social background. Dalton’s father was a weaver who came from a Quaker family (or also known as the Religious Society of Friends which was devoted to Protestants).

Dalton has two siblings, one of whom has an eye defect (color blindness) just like him.

Before discovering Dalton’s law, he worked as a teacher. When he was 12 years old, Dalton already had a job as a teacher at a Quaker School in his hometown to help support the family’s economy. He was also a farmer before returning to teaching at a Quaker school in Kendal.

At this school in Kendal, Dalton managed to get the position of headmaster. Later, Dalton also became a mathematics and philosophy tutor at New College, Manchester in 1793. Dalton also joined the Manchester Literary and Philosophical Society, then began his career as a scientist there.

Initially, Dalton was researching atomic weight, then he suddenly got the idea to research compounds.

In 1802, in his book entitled “On the Proportion of the Several Gases in the Atmosphere”, Dalton wrote that “The elements that make up oxygen can be combined with a certain amount of nitrogen gas or double the number of parts, but in the absence of an intermediate quantity.

Well, it is supported by the Law of Conservation of Mass (Lavoisier’s Law) and also the Law of Fixed Comparison (Proust’s Law) which existed before. Dalton became increasingly convinced about the Law of Multiple Comparisons. In 1804, Dalton officially published his ideas about the law.

John Dalton through various studies that he conducted both qualitatively and also quantitatively, Dalton discovered various things that are still relevant today. This was obtained from the results of studying with various experts in their fields. Some of his discoveries, among others;

  • Dalton’s atomic theory
  • Atomic sign
  • Find the cause of the rain
  • Pioneer of the science of meteorology or the science of predicting the weather
  • The law of double proportions in compounds
  • And others


In the theory he put forward, Dalton mentioned several things which later became the basis for studying chemistry. The contents of Dalton’s Law, namely:

1. Sound of Dalton’s Law

“If two elements can compose or form more than one compound, then the ratio of the mass of one element in those compounds is a simple integer when the mass of the other element is kept constant.”

2. Definition of Atoms

Dalton defined that every matter consists of molecules. While the molecule itself, consists of atoms. Atom is the smallest part of matter that can not be divided anymore. If a compound can be broken down and form a new compound, it is not the case with atoms. The combination of atoms can form a molecule or compound, while atoms cannot be broken down at all.

See also  Examples of Gases: Definition, Properties, and Processes of Change

3. Atomic Structure

In addition to making definitions of atoms, Dalton also conducted research on atomic structure. The results of Dalton’s research show that atoms have a solid spherical shape, where the edges tend to be denser when compared to the middle.

This atom consists of three charges namely, positive charge, negative charge, and also a neutral charge. From this research, then other researchers can show how molecules and compounds can be formed. Besides that, in the theory of atomic structure, Dalton also explained that each atom has a different structure from other atoms or can be referred to as “unique”. The H atom has a different structure from the C atom, and the O atom for example. This then allows people to know what is contained in a compound.

4. Compound Formation

As mentioned in the previous explanation, atoms can react with different atoms or with the same atom and form a compound. The formation of these compounds was also described by Dalton.

Dalton’s theory stated that atoms form a compound using simple spherical ratios, if one of the constituent elements is constant. Dalton’s basic law is also called the law of multiple comparisons which in theory contradicts Proust’s law of fixed comparisons.

5. Chemical Reaction

After declaring the law of multiple comparisons, Dalton also explained a chemical reaction. Chemical reactions can occur due to the separation and also the combination of atomic elements contained in a compound. In this reaction each atom is not destroyed, but combines with other atoms.

Dalton also proved that Lavoiser’s theory of conservation of mass, atoms can neither be destroyed nor created. If a new atom is discovered in the world, it does not mean that the new atom was actually just created but an atom that is only known to humans even though it has existed for a long time.

Chemistry is not the same as social sciences or physics and also the nature of biology. All theories in chemistry are indirectly related to everyday life. Therefore, chemical theory tends to be more difficult to understand.

An example of the theory of multiple comparisons, which practically means that the pressure of a mixture of a substance is the sum of the partial pressures of each substance that forms it. At a constant amount of volume, the amount of pressure will increase, so the partial pressure also increases. This also applies to the mixture of nitrogen, oxygen and pure gas used by divers. Thus, the tools used to enter the sea with higher pressure will provide information about how far the maximum depth that can be reached.

6. Dalton’s Law Restrictions

The law of multiple comparisons should be proven using simple compounds. This law does not work for non stoichiometric compounds, oligomers and polymers.

For example, carbon reacts with oxygen to form carbon dioxide (CO2) and carbon monoxide (CO). If the amount of carbon that reacts in each compound is 1 gram, then when observed in the carbon monoxide compound formed it will contain 1.33 grams of oxygen and also 2.67 grams of oxygen in the carbon dioxide compound. The mass ratio of oxygen is close to 2:1, which is a simple integer and obeys the law of multiple proportions.

7. Dalton’s Law Calculation Principles

There are two stages of determining the ratio of the mass of elements according to Dalton’s law.

1. Internal comparison

If there is a compound consisting of element A and element B with different proportions then:

If you want to determine the ratio of the mass of A to that contained in the two compounds, first determine the mass of B for each 1 gram of each compound. The trick is to divide the mass of B by the mass value of B and then divide the mass of A by the mass value of B.

If you are going to determine the mass ratio of B in the two compounds, first determine the mass of A in each 1 gram of each compound. The trick is to divide mass A by the value of mass A and then divide mass of B by the value of mass A.

2. External comparison

Because one of the elements has been made fixed, which means that the mass of one of the elements is made equal to 1 g or 1% or 1 part, the ratio of the masses of other elements can be determined from among their compounds.

See also  Getting to Know Export Import: Definition, Purpose, Benefits and Commodities

The way to get the results of the comparison is to divide it by the GCF (largest common factor) or the number dividing the second mass of the element.

According to the law of multiple comparisons the arithmetic result of the external comparison will always be a simple integer. The meaning of this simple number word is of course not limited to hundreds or even more. If you get a large number, it would be better if you check it again or round it off so that you get a round and simple comparison.

8. Another Example of Applying Dalton’s Law in Counting

1. Carbon and Oxygen

Carbon and Oxygen in chemistry have two types of bonds. The first is to form carbon monoxide or CO compounds. While the second compound forms carbon dioxide or CO 2  . Substances that are also known in everyday life as a result of the respiratory system by humans and animals.

In CO compounds, C and O have a ratio of 3: 4 and the ratio of C and O in CO 2 compounds  is 3: 8.

Note that the amount of C in both compounds is the same. According to Dalton’s law, the ratio between the masses of O from the two compounds, namely 4: 8 or 1: 2. This corresponds to the number of O atoms in CO and CO 2  .

2. Sulfur and Oxygen

Compounds combined between sulfur and oxygen are called sulfates and sulfites. When written in chemical formulas, namely SO 2  and SO 3 . The sulfur atoms present in both compounds have the same number of compounds, so that the mass ratio of O present in the two compounds is 2: 3, according to the mass whose coefficient has been shown.

3. Hydrogen and Oxygen

Hydrogen and oxygen also form two compounds that exist in nature, namely H 2 O and also H 2 O 2 . The number of hydrogen atoms in the two compounds is the same so that the hydrogen atoms in both have a fixed ratio, namely 1: 2.



So that we can understand better, here are some examples of problems and discussion of Dalton’s law.

Soal no. 1

Carbon and hydrogen can form methane, the ratio of which is 3:1. What mass of carbon is required to react with 200 grams of H in methane?

Answer :

Comparison of C : H = 3 : 1

So, the mass of C reacting with H is 3/1 x 200 grams = 600 grams.

Soal no. 2

Nitrogen and oxygen can form NO and NO2 compounds. Under certain conditions, 2 grams of nitrogen can react with 2.28 grams of oxygen and under other conditions 2 grams of nitrogen can react with 4.56 grams of nitrogen. Explain the data information using Dalton’s law!


In the first condition, the ratio of nitrogen and oxygen is 2 ; 2.28, while in other conditions the ratio is 2: 4.56.

Note that in both compounds, the number of atoms of nitrogen is the same, namely 2 grams. From this, it means that the ratio of oxygen present in the first condition and in the second condition is 2.28 : 4.56 = 1:2.

Soal no. 3

When there is an element of hydrogen and oxygen both of which can react to form water which is in a normal state. However, these two elements can also form hydrogen peroxide when they are in a state of high electrical energy.

Meanwhile, water contains 11.2% hydrogen and 88.8% oxygen. Meanwhile, hydrogen peroxide contains 5.93% hydrogen and 94.07% oxygen.

Answer :

In the water

For in the water alone about 11.2 grams of hydrogen which combines with 88.8 grams of oxygen. If stated according to Dalton’s law, 1.0 grams of hydrogen will combine with approximately 88.8 or 11.2 or expressed as 7.93 grams of oxygen.

Inside Hydrogen Peroxide

About 5.93 of the hydrogen combines with about 94.07 grams of oxygen. In 1.0 grams of hydrogen combined with approximately 94.07 or 5.93 or it can also be expressed with 15.9 grams of oxygen.

In hydrogen peroxide itself, the weight of oxygen for the hydrogen bond is around 15.9, or it can be said to be twice as much as the oxygen weight of the hydrogen bond that is already in the water itself.

So it can be stated that the same weight of hydrogen as the weight of oxygen in the peroxide compound is about twice the weight of oxygen in the water.