Chemistry

Atoms and Molecules


Explanation of the Law of Conservation of Mass


According to Dalton's atomic theory, atoms can neither be created nor destroyed.Now,since an atom cannot be created or destroyed,therefore, the number of various types of atoms m the products of a chemicalreaction is the same as the number of all those atoms in the reactants.The same number of various atoms in products and reactants will have the same mass.So, the total mass of products is equal to the total mass of reactants.The mass remains the same (or conserved) in a chemical reaction.And this is the law of conservation of mass. This explanation will become more clear from the following example of calcium carbonate.Calcium carbonate (CaCO3) is made up of 1 calcium atom, 1 carbon atom and 3 oxygen atoms. The products of its decomposition, calcium oxide (CaO)and carbon dioxide (CO2),taken together, also contain 1 calcium atom, 1 carbon atom and 3 oxygen atoms.Now,since the number of various types of atoms in the products (CaO and CO2) and reactant (CaCO3) remains the same,therefore, the mass of products and reactants also remains the same in this reaction. There is no change in mass during the decomposition of calcium carbonate to form calcium oxide and carbon dioxide. The mass remains conserved.

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Notes
Atoms and Molecules - Notes
1. Drawbacks of Dalton’s Atomic Theory
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2. Monovalent Cations (Cations Having a Valency of 1+)
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3. Dalton’s Symbols of Elements
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4. Divalent Cations (Cations Having a Valency of 2+)
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5. Trivalent Cations (Cations Having a Valency of 3+)
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6. Formulae of Some Molecular Compounds
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7. An Important Discussion
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8. Molecular Formulae of Some Common Elements
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9. an example, let us give the significance of symbol C
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10. As an example, let us give the significance of the formula H2O
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11. Chemical Formulae
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12. 2. A Negatively Charged Ion is Known as Anion
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13. Molecules
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14. Molecular Mass
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15. Molecules of Compounds
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16. Explanation of the Law of Conservation of Mass
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17. Some Ionic Compounds
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18. Atoms, Molecules and Ions
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19. Atoms
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20. Formula Mass
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21. Mole of Molecules
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22. Formulae of Elements
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23. 1. A Positively Charged Ion is Known as Cation
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24. Simple Ions and Compound Ions (Polyatomic Ions)
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25. 1. Molecules of Elements
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26. Symbols of Elements
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27. Gram Atomic Mass And Gram Molecular Mass
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28. John Dalton
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29. Mole of Atoms
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30. Formulae of Compounds
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31. Ions
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32. Explanation of the Law of Constant Proportions
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33. Dalton's Atomic Theory
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34. Significance of the Formula of a Substance
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35. Some Common Ions
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36. Molecular Masses of Some Common Elements
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37. Ionic Compounds
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38. Laws Of Chemical Combination
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39. Calculation of Molecular Mass
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40. Formula Unit of Ionic Compounds
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41. Divalent Anions (Anions Having a Valency of 2-)
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42. Atoms And Molecules
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43. How Do Atoms Exist
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44. Writing Of Formulae Of Ionic Compounds
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45. Problems Based On Moles Of Molecules
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46. Experiment to Verify Law of Conservation of Mass
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47. Gram Molecular Mass
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48. Gram Atomic Mass
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49. Laws Of Conservation of Mass
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50. Atomic Radii of Some Common Elements
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