law of multiple proportions assignment

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Law of Multiple Proportions – Dalton’s Law

In chemistry, the law of multiple proportions states that when two elements form more than one compound , the ratio of the different masses of one element that combine with a fixed mass of the other element are a ratio of small whole numbers. Another name for the law of multiple proportions is Dalton’s law , as John Dalton was the first chemist who described the law . However, Dalton also formulated Dalton’s law of partial pressures , so the “law of multiple proportions” is the preferred name.

Examples of the Law of Multiple Proportions

For example, Dalton observed that carbon forms two oxides by combing with oxygen in different proportions. For example, a 100-gram sample of carbon reacts with 133 grams of oxygen and forms one compound or with 266 grams of oxygen and forms the other compound. The ratio of oxygen masses that react with 100 grams of carbon is 266:133 = 2:1. From this data, Dalton predicted the chemical formulas for the two compounds are CO and CO 2 .

As another example, nitrogen reacts with oxygen, forming five different nitrogen oxides. The masses of oxygen that combine with 14 grams of nitrogen are 8, 16, 24, 32, and 40 grams. The ratio of oxygen masses is 1:2:3:4:5.

Law of Multiple Proportions Problems

There are two main types of law of multiple proportions problems. The first type of problem tests your understanding of the the concept. The other has you find the small number ratio between elements that form multiple compounds with another element.

Which of the following illustrates the law of multiple proportions?

• Ordinary water and heavy water
• Sodium chloride and sodium bromide
• Sulfur dioxide and sulfur trioxide
• Caustic soda and caustic potash

The correct answer is that sulfur dioxide and sulfur trioxide illustrate the law. The reason is because this is one element (sulfur) that combines with a second element (oxygen) and forms more than one compound. Sodium chloride and sodium bromide as well as caustic soda and caustic potash are scenarios that involve two compounds, but these compounds don’t contain the same two elements. Ordinary water and heavy water are the same compound as each other, just using different hydrogen isotopes .

Carbon and oxygen form two compounds. The first compound is 42.9% carbon by mass and 57.1% oxygen by mass. The second compound is 27.3% carbon by mass and 72.7% oxygen by mass. Show that the ratios between the oxygen masses are consistent with the law of multiple proportions.

To solve this problem, show that the masses oxygen that combine with a fixed amount of carbon are a whole number ratio. Make life easy on yourself and assume you have 100 grams of each sample. Then, there are 57.1 grams of oxygen and 42.9 grams of carbon in the first sample. So, the mass of oxygen (O) per gram of carbon (C) is:

57.1 g O / 42.9 g C = 1.33 g O per g C

For the second compound, assuming a 100 grams sample, there are 72.7 grams of oxygen (O) and 27.3 grams of carbon (C). The mass of oxygen per gram of carbon is:

72.7 g O / 27.3 g C = 2.66 g O per g C

Setting up the problem this way makes the fixed amount of carbon equal to 1 gram. So, all you do is divide the mass of oxygen per grams of carbon for the two compounds:

2.66 / 1.33 = 2

In other words, the masses of oxygen that combine with carbon are in a 2:1 ratio. This small whole number ratio supports the law of multiple proportions.

Note it does not matter if you perform the calculation the other way (1.33 / 2.66 = 1 / 2 or a 1:2 ratio) because you still get a whole number ratio. Also, in actual experiments, you probably won’t get perfect data and may need to do a bit of rounding! For example, if your ratio comes out as 2.1 : 0.9, then you round the number to get a 2:1 ratio.

Limitations of the Law of Multiple Proportions

The law of multiple proportions best applies to simple compounds.

It does not work well in all circumstances or even apply to all compounds. Specifically, it fails for non-stoichiometric compounds, oligomers, and polymers. It does not work well for larger molecules that contain hydrogen. Hydrogen has such a small mass that rounding errors often give erroneous ratios, plus the ratios between hydrogen masses are not always small whole numbers.

For example, carbon and hydrogen form the hydrocarbons decane (C 10 H 22 ) and undecane (C 11 H 24 ). For 100 grams of carbon, decane has 18.46 grams of hydrogen and undecane has 18.31 grams of hydrogen. The ratio of hydrogen masses between the two compounds is 121:120, which is not a small whole number ratio.

The law of multiple proportions is important because it ties in with Dalton’s atomic theory. However, it is unclear whether Dalton observed the law of multiple proportions and then used it to formulate his atomic theory or whether the theory came first.

While Dalton first described the law, he was not the first chemist to observe it in action. In 1792, Bertrand Pelletier noted that a fixed amount of oxygen forms one type of tin oxide and twice that amount of oxygen (ratio of 1:2) forms a different oxide. Joseph Proust confirmed Pelletier’s observations and measured the relative amounts of tin and oxygen in the compounds. While Proust had the necessary information to discover the law, he did not generalize his findings.

• Pelletier, Bertrand (1792). “ Observations sur plusieurs propriétés du Muriate d’Étain ” [Observations on various properties of muriate of tin]. Annales de Chimie (in French). 12: 225–240.
• Petrucci, Ralph H.; Harwood, William S.; Herring, F. Geoffrey (2002). General Chemistry: Principles and Modern Applications (8th ed.). Upper Saddle River, N.J: Prentice Hall. ISBN 978-0-13-014329-7.
• Proust, Joseph Louis (1800). “ Recherches sur l’étain ” [Research on tin]. Journal de Physique, de Chimie, et d’Histoire Naturelle (in French). 51: 173–184.
• Roscoe, Henry E.; Harden, Arthur (1896). A New View of the Origin of Dalton’s Atomic Theory . Macmillan and Co.

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law of multiple proportions

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law of multiple proportions , statement that when two elements combine with each other to form more than one compound , the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers. For example, there are five distinct oxides of nitrogen , and the weights of oxygen in combination with 14 grams of nitrogen are, in increasing order, 8, 16, 24, 32, and 40 grams, or in a ratio of 1, 2, 3, 4, 5. The law was announced (1803) by the English chemist John Dalton , and its confirmation for a wide range of compounds served as the most powerful argument in support of Dalton’s theory that matter consists of indivisible atoms .

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• Law of Multiple Proportions

State the Law of Multiple Proportion?

In chemistry, the law of multiple proportions can be defined as if two elements form more than one compound between them, the mass ratios of the second element that combine with a fixed mass of the first element will always be the ratios of small whole numbers. Sometimes, this law is referred to as Dalton's Law (or Dalton's Law of multiple proportions) because it is named after John Dalton, the chemist who expressed it first.

The Law of Multiple Proportions is defined as:  “if two elements combine to form more than one compound, the mass ratios of the second element that combine with a fixed mass of the first element will always be ratios of minuscule whole numbers.” This law, sometimes known as Dalton's Law or Dalton's Law of Multiple Proportions, was proposed by Dalton in 1803.

Hydrogen, for example, reacts with oxygen to generate two compounds: water and hydrogen peroxide.

Hydrogen + Oxygen → Water 

Hydrogen + Oxygen → Hydrogen Peroxide

Examples of Law of Multiple Proportions

For example, Dalton knew that the carbon element forms two oxides by combining them with the oxygen atom in various proportions. A fixed mass of carbon compound, let us suppose 100 grams, can react with 266 grams of oxygen to form one oxide atom or with 133 grams of oxygen to form the other. The ratio of the oxygen masses that can react with the 100 grams of carbon is given as 266:133 = 2:1, which is a ratio of small whole numbers. Dalton has interpreted these results in his atomic theory by proposing that the two oxides have one oxygen atom and two oxygen atoms, respectively, for every carbon atom. In modern notation, the first is given as CO ( carbon monoxide ), and the second is given as \[CO_{2}\] ( carbon dioxide ).

First, John Dalton expressed this specific observation in 1804. But, a few years before, the French chemist named Joseph Proust had proposed the law of definite proportions, which has expressed that the elements combined to produce compounds in certain well-defined proportions, instead of mixing in just any proportion. And, Antoine Lavoisier has proved the law of conservation of mass that helped out Dalton. A careful study of the exact numerical values of these proportions has led Dalton to propose his law of multiple proportions. This was an essential step toward the atomic theory that he would propose later the same year, and it laid the basis for the compound's chemical formulas.

Another example of the law is seen by comparing the ethane (\[C_{2}H_{6}\]) compound with the propane (\[C_{3}H_{8}\]) compound. The weight of hydrogen that combines with 1 gram carbon is 0.252 gram in the ethane and 0.224 gram in the propane. The ratio of those weights is 1.125, which is equal to the ratio of two small numbers (9:8).

Dalton’s Atomic Theory

Democritus has first suggested the atom's existence. However, it took almost two centuries for the atom to be established as a basic chemical entity, which was accomplished by John Dalton (from the years 1766-1844). Dalton's atomic theory remains valid in modern chemical thought, although two centuries old.

Important Points of Dalton's Atomic Theory

All atoms of the given element are identical in properties and mass

All matter is completely made of atoms, and these atoms are indestructible and indivisible

A chemical reaction is given as a rearrangement of atoms

Compounds are produced by the combination of either two or more various kinds of atoms

Modern atomic theory is given as a little more involved than Dalton's theory. But, the essence of Dalton's theory remains completely valid. Currently, we know that atoms are destroyed by nuclear reactions but not by chemical reactions. Also, there are various kinds of atoms (differ by their masses) within an element that are called "isotopes", but the isotopes of an element contain similar chemical properties.

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Several heretofore unexplained chemical methods were quickly explained by Dalton with his specific theory. In chemistry, Dalton's theory very quickly became the theoretical foundation.

To put it simply and briefly, the atomic structure of a compound is a vital component to understanding the behavior and reactivity of chemicals. Simply by looking at the structure of a molecule , a chemist can be able to predict several things about a chemical such as :

Boiling points and melting points

Acidity or basicity

Reactivity with the other compounds

What sort of products that two chemicals might produce in a chemical reaction

The list goes on. Not only are there easy and simple ways to predict the properties of compounds, but there are also things that wouldn't be obvious immediately. As an example, several molecules will contain two forms, which are mirror images of each other (which can be based on the arrangement where the molecules are bonded). Every mirror image contains drastically different effects, like in Thalidomide. One mirror image of this molecule can be used as a useful drug, but also the other image, as it turned out, was a carcinogen.

Basically, both the short and long of it is that if we understand the atomic structure of a compound, we can rationalize the effects that we didn't necessarily predict and predict its chemical behavior.

The law of multiple proportions is a fundamental rule of chemistry. According to the law of multiple proportions, if two elements can react to produce several compounds, the ratio of their masses that mix with a fixed mass of the other element is in the ratio of tiny whole numbers. It was instrumental in the early understanding of stoichiometry, along with the law of definite proportions. The concept was proposed in 1803, by English chemist John Dalton, who is best known for his partial pressures law. Dalton stated the law in his book New System of Chemical Philosophy (Vol 1).

Proust's law of definite proportions was followed by the law of multiple proportions. The law backed up Proust's work and later aided Dalton in his atomic theory.

FAQs on Law of Multiple Proportions

1. What are the limitations of the Law of Multiple Proportions?

The law of multiple proportions is demonstrated best using simple compounds. For example, if anyone tried to demonstrate the same using the hydrocarbons decane (having the chemical formula (\[C_{10}H_{22}\])) and undecane (with the chemical formula (\[C_{11}H_{24}\])), one would find that 100 gms of carbon could react with 18.46 grams of hydrogen to form decane or with 18.31 gms of hydrogen to form undecane, for the ratio of hydrogen masses about 121:120, which is a hard ratio of "small" whole numbers.

This law fails with the compounds of non-stoichiometric type and also does not work well with oligomers and polymers.

2. What is the difference between the Law of Definite Proportions and the Law of Multiple Proportions?

The law of definite proportions asserts that samples of a compound will always contain the same mass proportion of constituents, as opposed to the law of multiple proportions. 

As per the Law of Multiple proportions commonly known as Dalton’s Law, when two elements unite to form more than one chemical compound, the ratio of the mass of the second element combined with a fixed mass of the first element, it will be minuscule whole number ratios.

3. Give two examples of the Law of Multiple Proportions.

The examples are as follows:

Example 1: Carbon (C) and Oxygen (O) combine to form the compounds CO and \[CO_{2}\].

CO2 contains 12g of carbon and 16g of oxygen.

12g of C combined with 32g of O in \[CO_{2}\].

If the mass of C is fixed at 12g, the oxygen-to-mass ratio that combines with the fixed mass of C (12g) is 16: 32, or 1: 2.

As a result, the mass of oxygen bears a simple 1: 2 ratio to each other.

Example 2: Sulphate (S) and Oxygen (O) Compounds:

S reacts with O to form two oxides, \[SO_{2}\] and \[SO_{3}\].

\[SO_{2}\] is formed when 32g of S and 32g of O combine.

\[SO_{3}\] is formed when 32g of S and 48g of O combine.

If the mass of S is fixed at 32g, the mass of oxygen that combines with the fixed mass of S is 32: 48, or 2: 3.

As a result, the mass of oxygen bears a simple 2: 3 ratio to each other.

4. List the shortcomings of Dalton’s atomic theory.

Some important demerits of Dalton’s atomic theory are listed below.

The presence of subatomic particles was not accounted for in the theory (it suggested that atoms are indivisible).

By suggesting that all atoms of an element must have identical masses and sizes, Dalton’s atomic theory did not account for the existence of isotopes. Isobars were not accounted for in this theory.

Dalton's atomic theory could not account for the differences in attributes between different allotropes of the same element.

To produce compounds, elements must combine in simple, whole-number ratios, according to this hypothesis. However, this isn't always the case. The constituent constituents of several complex organic molecules do not have simple ratios.

5. Is it true that electrons exist?

As most of us know, the neutron is a negatively charged particle that orbits the nucleus of an atom of matter. At any given time, no two electrons can occupy the same space. They can be found in any molecule, but they can also live on their own.

6. How can CBSE Class 11 students obtain free Law of Multiple Proportions questions and answers from Vedantu?

Students should be aware that the Class 12 Chemistry syllabus is extensive, and that to receive good grades, they must answer all of the important questions. The Vedantu website contains important Class 11 Chemistry questions on a variety of topics, including the Law of Multiple Proportions . This can also help 12th-grade students understand the principles of multiple chapters and improve their grades on the CBSE board’s final exam.

7. Give the Importance of Atomic Theory?

Knowing the atomic theory allows us to:

know the origin, predict the chemical properties and physical properties of the atom

know the atomic structure, including its electron configuration

understand and predict the nature of compounds, which are formed by different atoms

understand the Chemical Element's Periodic Table, its importance and structure in Chemistry

understand some methods like absorption and atomic light emission.

8. Give the Most Accepted Atomic Structure?

There is an important point about the Bohr model, which is no longer accepted in the current models of the atom. In this Bohr model, still, the electrons are thought to orbit the nucleus just as planets orbit the sun.

9. What is the Structure of an Atom?

The matter has mass and takes up space. Atoms are defined as basic building blocks of matter, and they cannot be chemically subdivided by ordinary means.

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Chemistry I

2.2 law of multiple proportions.

The Law of Multiple Proportions (Dalton’s Law) states that When two elements react, the mass of one element will react with masses of a second element so compounds always equals a ratio of small, whole number.

32 grams of O reacts with 24 grams of C

\[\mathrm{ratio} = \dfrac{\mathrm{O}}{\mathrm{C}} = \dfrac{32}{24} = 1.33\]

64 grams O reacts with 24 grams of C

\[\mathrm{ratio} = \dfrac{\mathrm{O}}{\mathrm{C}} = \dfrac{64}{24} = 2.66\]

\[\dfrac{\mathrm{Compound~A}}{\mathrm{Compound~B}} = \dfrac{2.66}{1.33} = \dfrac{2}{1}\]

Compound B has 2 O for every C; compound A has 1 O for every C.

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State and explain law of multiple proportions with the help of an example.

Law of multiple proportions: when two elements combine to generate more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of tiny whole numbers, according to the law of multiple proportions. the english scientist john dalton established the rule in 1803 ; its validation over a wide range of compounds is regarded as the most strong evidence in support of dalton's idea that matter is made up of indivisible atoms. example: let us assume two molecules co (carbon monoxide) and co 2 (carbon dioxide). co = 12 grams of carbon + 16 grams of oxygen . co 2 = 12 grams carbon + 32 grams of oxygen . the ratio of the mass of oxygen in the given two compounds is 16 : 32 = 1 : 2 thus, the law of multiple proportions is proved..

State and explain the law of constant proportions by giving an example.

What is law of multiple proportion ? Explain with an example clearly

Explain law of multiple proportion?

With examples