Step-by-Step Guide to Understanding the Law with Examples
German chemist Jeremias Richter devised a simple method for comparing compounds and determining how two elements will combine to make another chemical in the late 18th century.
Law of Reciprocal Proportion
Jeremias Ritcher put forward the law of reciprocal proportions in 1792. According to the law of reciprocal proportions, we may calculate the proportion of elements in compound AC if we know the proportion of elements in compounds AB and BC. This law aided in our understanding of stoichiometry, which is the process of calculating the amounts of reactants and products in relation to reactions.
History of The Scientist
Jeremias Benjamin Richter (1762 - 1807)
Name: Jeremias Benjamin Richter
Born: 10 March 1762
Died: 4 May 1807
Field: Chemist
Nationality: German
What is the Law of Reciprocal Proportion?
The rule of reciprocal proportions is another name for the law of reciprocal proportions, which is also referred to as the law of equivalent proportions or permanent ratios.
According to Ritcher, "When two elements combine independently with a fixed mass of the third element, the ratio of their masses at that time is either the same or some whole number multiple of the ratio they mix."
Law of Reciprocal Proportion Examples
Let's take methane and calculate the ratio of the components. Hydrogen has a molecular weight of 1 g/mol, and carbon has a molecular weight of 12 g/mol. Since there are 4 hydrogen atoms for every carbon atom, the ratio is 12:4, which can be expressed as 3:1.
Therefore, both hydrogen and another element can be found in methane and water. This law states that the ratio of carbon to oxygen, which makes up the other element in both molecules, should be 3:8, or a straightforward multiple of that ratio.
We obtain 3:8 because water has an oxygen to carbon ratio of 8, and methane has an oxygen to carbon ratio of 3. Let's check to see whether this is accurate: the ratio of carbon to oxygen in carbon dioxide is 12:32.
Let's look at another illustration, beginning with sodium chloride. The molecular weights of sodium and chloride are 23 and 35 g/mol, respectively. This makes the ratio 23:35.
Let's now examine hydrochloric acid with a 35:1 ratio. The ratio we would anticipate to observe if we combined salt and hydrogen is 23:1. Yes, these come together to produce sodium.
Limitations of Law of Reciprocal Proportion
Differences similar to those seen in the law of constant proportions are produced by the element's isotopes. The synthesis of a number of chemicals should thus use the same isotope or a combination of isotopes.
The law only applies to a tiny subset of products that exhibit the disputed property since there are only a finite number of elements that will combine with the third element and also with one another.
Applications of Law of Reciprocal Proportion
We can now understand stoichiometry thanks to this law. This is how the quantities of the reactants and products in relation to the reaction are calculated. The law that exists now makes sense because every element has a specific molecular weight. To create an elemental compound, each element is added in a ratio of whole numbers.
Solved Examples
1. What made the law of reciprocal proportions significant?
It aided in the discovery of novel chemicals
It contributed to our current understanding of stoichiometry.
It assisted scientists in determining complex sizes.
The periodic table was made possible by it.
Ans: The correct answer is option B. As the law of reciprocal proportions plays an important role in studying and understanding the basic rules of stoichiometry.
2. Carbon is found in three different compounds: carbon dioxide (27.27%), carbon disulfide (15.79%), and sulphur dioxide (50%) Clearly demonstrate how the data exemplifies the law of reciprocal proportions.
Ans:
Carbon Compound
Let us take Carbon dioxide.
The percentage of carbon is 27.27
Percentage of oxygen (100 – 27.27) is 72.73
27.27 g of carbon reacts with 72.73 g of oxygen.
1 g of carbon joins with 72.73 / 27.27 => 2.67 g of oxygen.
Let us take Carbon disulfide.
Percentage of carbon = 15.79
Percentage of sulphur (100 – 15.79) is 84.21
15.79 g of carbon reacts with 84.21 g of sulphur.
Hence, 1 g of carbon reacts with \[\frac{84.21}{15.79}\] = 5.33 g of sulphur.
The ratio of different masses of sulphur and oxygen joining with a fixed mass of carbon is 5.33: 2.67.
That is, 2: 1. —> [1]
Let us take Sulphur Dioxide,
Percentage of sulphur = 50
Percentage of oxygen = 100 – 50 = 50
50 g of sulphur reacts with 50 g of oxygen.
The ratio of the mass of sulphur to oxygen is 50: 50,
That is, 1:1 —> [2]
A straightforward whole-number multiple of the first ratio is the second ratio. The information serves as an example of the law of reciprocal proportions.
3. Different oxygen content ratios in the various nitrogen oxides demonstrate the following law:
The Law of reciprocal proportions
The Law of multiple proportions
The Law of constant proportions
The Law of conservation of mass
Ans: Option A offers the right response. The law of multiple proportions, which states that when two elements combine in more than one proportion to form one or more compounds, the weight of one element that combines with the given weight of other elements is in the ratio of the small whole number, is demonstrated by the different proportions of oxygen in the various oxides of nitrogen.
Important Points to Remember
The rule of reciprocal proportions is another name for the law of reciprocal proportions, which is also referred to as the law of equivalent proportions or permanent ratios.
One of the fundamental laws of stoichiometry, along with definite and various proportions laws, is this one.
German physicist Jeremias Richter proposed the statute in 1791.
Conclusion
With the law's consent, tables of equivalent element weights might be made. These equivalent weights were frequently used by chemists in the nineteenth century. Two further stoichiometric laws are the law of definite proportions and the law of many proportions. The law of definite proportions is the formula for any compound formed between components A and B.
FAQs on Law of Reciprocal Proportion in Chemistry
1. What is the Law of Reciprocal Proportions in chemistry?
The Law of Reciprocal Proportions states that if two different elements combine separately with a fixed mass of a third element, the ratio of the masses in which they do so is either the same or a simple whole-number multiple of the ratio in which they combine with each other. This law helps in understanding the combining capacities of elements, also known as their equivalent weights.
2. Can you explain the Law of Reciprocal Proportions with a simple example?
Certainly. Let's consider three elements: Hydrogen (H), Sulphur (S), and Oxygen (O).
- Hydrogen combines with Sulphur to form Hydrogen Sulphide (H₂S). Here, 2 grams of H combine with 32 grams of S.
- Hydrogen also combines with Oxygen to form Water (H₂O). Here, 2 grams of H combine with 16 grams of O.
According to the law, when Sulphur and Oxygen combine with each other (to form Sulphur Dioxide, SO₂), their mass ratio should be a simple multiple of 2:1. In SO₂, 32 grams of S combine with 32 grams of O, giving a ratio of 32:32 or 1:1. The ratio of these two results (2:1 and 1:1) is (2/1) / (1/1) = 2, which is a simple whole number, thus verifying the law.
3. Who first proposed the Law of Reciprocal Proportions?
The Law of Reciprocal Proportions was first proposed by the German chemist Jeremias Richter in 1792. His work laid the foundation for stoichiometry by observing the fixed ratios in which elements combine, which later helped in determining equivalent weights of elements.
4. Why is the Law of Reciprocal Proportions also known as the Law of Equivalent Proportions?
This law is also called the Law of Equivalent Proportions because it deals with the masses of elements that are chemically equivalent to a fixed mass of another element. The concept of equivalent weight is a direct consequence of this law. The equivalent weight of an element is the mass that combines with or displaces 1 part by mass of hydrogen, 8 parts by mass of oxygen, or 35.5 parts by mass of chlorine. The law shows that elements combine in the ratio of their equivalent weights or simple multiples thereof.
5. How is the Law of Reciprocal Proportions different from the Law of Multiple Proportions?
The key difference lies in the number and combination of elements being compared:
- The Law of Reciprocal Proportions involves three different elements. It compares the mass ratios of two elements (A and B) combining with a fixed mass of a third element (C), and then relates that to the ratio when A and B combine directly.
- The Law of Multiple Proportions involves only two elements. It states that if two elements form more than one compound, the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers. For example, in H₂O and H₂O₂, the masses of oxygen that combine with a fixed mass of hydrogen are in a simple 1:2 ratio.
6. What is the main significance of the Law of Reciprocal Proportions in the development of chemistry?
The primary significance of the Law of Reciprocal Proportions is that it provided strong evidence for the concept of equivalent weights. It helped chemists to establish a system of relative combining weights for different elements long before the atomic theory was fully accepted. This was a crucial step in the development of the periodic table and the field of stoichiometry, as it allowed for the quantitative analysis of chemical reactions.
7. Are there any limitations or exceptions to the Law of Reciprocal Proportions?
The Law of Reciprocal Proportions, like other laws of chemical combination, holds true for most chemical reactions but has some specific limitations:
- Isotopes: The law does not account for the existence of isotopes. Since elements can have isotopes with different masses, the mass ratios may not be perfectly fixed if different isotopic compositions are used. However, this effect is often negligible due to the constant natural abundance of isotopes.
- Non-Stoichiometric Compounds: The law is not applicable to non-stoichiometric compounds (also known as Berthollides), where the ratio of elements can vary over a certain range without changing the substance's phase.
