Laws Of Conservation of Mass
In the 18th century, scientists noticed that if they carried out a chemical reaction in a closed container, then there was no change of mass. This preservation of mass in a chemical reaction led to the formulation of the law of conservation of mass (or law of conservation of matter). Law of conservation of mass was given by Lavoisier in 1774. According to the law of conservation of mass : Matter is neither created nor destroyed in a chemical reaction. The substances which combine together (or react) in a chemical reaction are known as 'reactants' whereas the new substances formed (or produced) as a result of chemical reaction are called 'products'. The law of conservation of mass means that in a chemical reaction, the total mass of products is equal to the total mass of reactants. There is no change in mass during a chemical reaction. Since there is no gain or loss in mass in a chemical reaction, the mass remains conserved. Please note that the term 'total mass' of reactants and products includes solids, liquids and gases - including air - that are a part of the reaction. The law of conservation of mass will become clear from the following example.
When calcium carbonate is heated, a chemical reaction takes place to form calcium oxide and carbon dioxide. It has been found by experiments that if 100 grams of calcium carbonate are decomposed completely then 56 grams of calcium oxide and 44 grams of carbon dioxide are formed. This can be written as :
In this example, calcium carbonate is the reactant and it has a mass of 100 g. Calcium oxide and carbon dioxide are the products and they have a total mass of 56 g + 44 g = 100 g. Now, since the total mass of products (100 g) is equal to the total mass of reactant (100 g), there is no change of mass during this chemical reaction. The mass remains the same or conserved.So, this example supports the law of conservation of mass.
We can verify the law of conservation of mass in the laboratory by taking known masses of two chemicals (reactants), allowing them to react by mixing them, and then finding the masses of the products formed. There should be no change in the mass. This will become more clear from the following experiment in which we will carry out a chemical reaction between barium chloride and sodium sulphate to form barium sulphate and sodium chloride.
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Atoms and Molecules - Notes
2. Monovalent Cations (Cations Having a Valency of 1+)
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3. Divalent Cations (Cations Having a Valency of 2+)
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4. Trivalent Cations (Cations Having a Valency of 3+)
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6. an example, let us give the significance of symbol C
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7. Formulae of Some Molecular Compounds
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9. Molecular Formulae of Some Common Elements
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10. Explanation of the Law of Conservation of Mass
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11. 2. A Negatively Charged Ion is Known as Anion
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13. As an example, let us give the significance of the formula H
2O
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14. Simple Ions and Compound Ions (Polyatomic Ions)
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21. Gram Atomic Mass And Gram Molecular Mass
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28. 1. A Positively Charged Ion is Known as Cation
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34. Divalent Anions (Anions Having a Valency of 2-)
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35. Molecular Masses of Some Common Elements
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37. Explanation of the Law of Constant Proportions
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39. Significance of the Formula of a Substance
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42. Symbols Derived from Latin Names of the Elements
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45. Valencies of Some Common Metal Elements Valencies of Some Common Non-Metal Elements
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46. Atomic Masses of Some Common Elements
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47. Writing Of Formulae Of Molecular Compounds
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50. Writing Of Formulae Of Ionic Compounds
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