what are two processes by which elements can combine to form stable compounds
In chemical science, a matter is transformed from ane class to the other to form different types of thing. These combinations of different matters are governed by certain basic rules. These rules are referred to as laws of chemical combination. The Law of Multiple Proportions is amid i of the Laws of Chemical Combinations.
The Topic 'Law of Multiple Proportions' falls under Unit 1 of CBSE Class eleven Chemical science. As per the revised syllabus, Unit 1 and Unit of measurement 2 carries a combined weightage of 11 Marks in the CBSE Class xi Examination.
Read Also: Periodic Classification of Elements
Law of Multiple Proportions
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The Law of Multiple Proportions states that "If two elements combine to form more than one chemical compound betwixt them, the mass ratios of the second element which combine with a fixed mass of the first element will always be the ratios of small whole numbers."
This law was proposed by Dalton in 1803 and is also known every bit Dalton'due south Law or Dalton'due south Law of multiple proportions.
For example, Hydrogen combines with oxygen to course two compounds, ane water, and some other hydrogen peroxide.
Hydrogen + Oxygen → Water
2g 16g 18g
Hydrogen + Oxygen → Hydrogen Peroxide
2g 32g 34g
Here, the masses of Oxygen are 16g and 32g and Hydrogen's fixed mass is 2g with a simple ratio of xvi:32 or 1:two in both cases.
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Examples of Police of Multiple Proportions
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Dalton understands that a carbon element combining with an oxygen atom in various proportions forms two oxides. Carbon's fixed mass, let us consider 100g can react with 266g of oxygen to class one oxide atom or with 133g of oxygen to class the other.
The ratio of the oxygen masses that tin react with carbon, is given equally 266:133 = ii:one, which is the ratio of minor whole numbers.
Read More: Analytical Chemistry
Dalton has proposed that the two oxides accept ane oxygen atom and two oxygen atoms, respectively, for every carbon atom in his atomic theory. In modern note, the first atom is CO (carbon monoxide), and the other is CO2 (carbon dioxide).
Some other example of the police force of multiple proportions can be explained by comparing the ethane (C2H6) compound with the propane (C3H8) compound. Hydrogen's weight combined with 1g carbon is 0.252 one thousand in the ethane and 0.224 grand in the propane. The ratio is 1.125, which is equal to the ratio of two small numbers (9:8).
Limitations of Constabulary of Multiple Proportions
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- The Police of Multiple proportions is valid till an chemical element is present in one detail isotopic form in all its compounds.
- When an element exists in the form of different isotopes in its compounds, the Law of Multiple proportions does not concord well.
Read More than: Anode and Cathode Important Notes
Police force of Multiple Proportions: Dalton'south Atomic Theory
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Atom's existence was first suggested by Democritus. But it took most two centuries to establish the atom every bit a basic chemical entity, which was proposed by John Dalton.
Police force of Multiple Proportions: Important Points of Dalton'due south Atomic Theory
- All atoms of an chemical element are identical in mass and backdrop.
- Atoms are indestructible and indivisible.
- A chemical reaction can represent the rearrangement of atoms.
- Compounds are produced by the combination of more than one multifariousness of atoms.
Dalton's theory is valid in modern chemistry as well. Information technology explains that atoms are destroyed by nuclear reactions but not by chemical reactions. In that location are a variety of atoms that differ by their masses, within an element that are called "isotopes", simply the element's isotopes incorporate similar chemical properties.
Various chemical methods were quickly explained past Dalton in his theory and became the theoretical foundation in chemistry.
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Of import Questions Based on Law of Multiple Proportions
Ques: The post-obit data are obtained when dinitrogen and dioxygen react together to form unlike compounds:
| Mass of dinitrogen | Mass of dioxygen |
|---|---|
| 14g | 16g |
| 14g | 32g |
| 28g | 32g |
| 28g | 80g |
Ques: Which law of chemical combination is obeyed by the above experimental data? Give its statement.(2 Marks)
Answer: The experimental information obey the Law of Multiple Proportions. It was proposed past Dalton in 1803. It states that "If two elements can combine to class more than than one compound the masses of one element that combine with a fixed mass of the other chemical element are in the ratio of small-scale whole numbers."
Considering the mass of dinitrogen as 28 g, masses of dioxygen combined will be 32, 64, 32, and 80 g in the given four oxides. These are in the ratio of 2: 4: ii: 5 which is a elementary whole-number ratio. Hence, the given data obeys the law of multiple proportions.
Ques: Explain the law of multiple proportions with an example.(ii Marks)
Answer: The constabulary of multiple proportions states that "if two elements can combine to form more than than i compound, the masses of i element that combine with a fixed mass of another chemical element, are in a ratio of small whole numbers. For Example, hydrogen and oxygen can combine to form water equally well as hydrogen peroxide.
Here, the masses of oxygen (16g & 32g) are combined with a fixed mass of hydrogen (2g) to give a simple ratio i.e., sixteen:32 = i:2
Ques: Give two examples of the Law of Multiple Proportions.(ii Marks)
Answer: Police force of Multiple Proportions-
- The chemical compound of Carbon and Oxygen: C and O combine to form ii compounds CO and CO2.
In CO2,12g of C combined with 16g of O.
In CO2, 12g of C combined with 32g of O.
If the mass of C is fixed at 12g then the ratio of oxygen which combines with the stock-still mass of C (12g) is sixteen: 32 or 1: 2.
Thus the mass of oxygen bears a simple ratio of 1: ii to each other.
- Compounds of Sulphate (S) and Oxygen (O): S forms two oxides with O, viz., SOii and SO3
In SO2, 32g of S combines with 32g of O.
In And then3, 32g of S combines with 48g of O.
If the mass of S is stock-still at 32g, then the ratio in the mass of oxygen which combines with the stock-still mass of Due south is 32: 48 or 2: 3.
Thus the mass of oxygen bears a simple ratio of ii: 3 to each other.
Ques: Which of the following statements indicates that the law of multiple proportions is being followed?
(a) Sample of carbon dioxide taken from whatsoever source will ever have carbon and oxygen in the ratio 1:2.
(b) Carbon forms ii oxides namely C0 2 and CO, where masses of oxygen that combine with a fixed mass of carbon are in the simple ratio two:1.
(c) When magnesium burns in oxygen, the amount of magnesium taken for the reaction is equal to the amount of magnesium in magnesium oxide formed.
(d) At abiding temperature and pressure, 200 mL of hydrogen will combine with 100 mL oxygen to produce 200 mL of water vapor.(2 Marks)
Answer: Statement (b) follows the Law of Multiple Proportion
Carbon combines with oxygen to form ii compounds- carbon dioxide and carbon monoxide. In CO2, 12 parts by mass of carbon combine with 32 parts past mass of oxygen while in CO, 12 parts by mass of carbon combine with 16 parts by mass of oxygen.
Therefore, the masses of oxygen combined with a stock-still mass of carbon (12 parts) in C02 and CO are 32 and 16 respectively. These masses of oxygen conduct a elementary ratio of 32 : 16 or 2 : 1 to each other.
Ques: Give the Limitations of the Law of Multiple Proportions.(2 Marks)
Answer: ane. The law of multiple proportions fails with the compounds of non-stoichiometric, Oligomers, and Polymers.
- The Law of Multiple proportions is valid till an element is present in one detail isotopic class in all its compounds. When an element exists in the form of dissimilar isotopes in its compounds, the Law of Multiple proportions does not hold well.
Ques: How does this law of multiple proportions point to the being of atoms?(2 Marks)
Respond: Law of multiple proportions shows that there are constituents that combine in a definite proportion. These constituents may be atoms. Thus, the constabulary of multiple proportions shows the existence of atoms that combine to form molecules.
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