Law of conservation of mass 1


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Law of conservation of mass 1

  1. 1.  In the late eighteenth century, Antoine Lavoisier, a French chemist, recognized the importance of accurate measurements. He extensively studied and explained the nature of combustion. He found out that combustion involved reaction with oxygen.
  2. 2. Law of Conservation of Mass Mass is neither created nor destroyed during chemical or physical reactions. Antoine Lavoisier Total mass of reactants = Total mass of products
  3. 3.  Reactants are the starting material in a chemical reaction.  Products are the substance formed as a result of a chemical reaction.  In a chemical equation, reactants are found on the left side and the products are on the right side. A chemical reaction can therefore be summarized as: Reactants → Products
  4. 4. sodium metal + chlorine gas ---- table salt (sodium chloride)
  5. 5. The Law of conservation of mass states that matter cannot be created or destroyed in any chemical reaction The atoms in the reactants are rearranged to form new compounds, but none of the atoms disappear, and no new atoms are formed. H H H H O Reactants O Products
  6. 6. Al Al Al Al O O O O O O O Al O Al O O Al O Al O
  7. 7. Balancing an equation: O2  2 H2 + H H O O 2 H2O H O H Second: Determine which atoms are sides of and First: Inventory the atoms on both not equalthe add coefficients to balance these atoms. yield arrow Hydogen Hydogen 4 H atoms 2 H atoms 4 2 H atoms H atoms atoms are ≠ atoms are = 2 O atoms 2 O atoms Oxygen Oxygen 2 1 O atom O atoms atoms are atoms are≠= atoms are = When a coefficient is added you must multiply 2. After redoing the balancedmultiplied by Oxygen,is now a inventory, add coefficients be equation This inas a product, mustthis number. allA coefficient compound in With each additional atoms the is placed by to balanced other atoms. front of the Redo the inventorycontains O. coefficient the compounds that inventory must be updated.
  8. 8. So: Chemical equations are balanced, when the numbers and kinds of atoms on each side of the reaction arrow are equal. H H H H O H O O H H Reactants Products 4 Hydrogen 4 Hydrogen 2 Oxygen 2 Oxygen H O
  9. 9. Because atoms are conserved, the mass of the reactants in the chemical reaction is equal to the mass of the products. H2 + F2 H F 2g H+ 38g 40g  F 2 HF H F = 2( 20g) = 40g Reactants H Products 40 g 40 g F
  10. 10. If 27.0 g of mercuric oxide (the red solid compound) is heated and completely decomposes to give the elements oxygen and mercury. 2.0 g of oxygen are produced. How many grams of mercury are produced? mercuric oxide  mercury + oxygen HgO  Hg + O2
  11. 11. 2.0 g O2 27.0 g HgO ? g Hg 27 g HgO = 2 g O2 + ? Hg = 25 g Hg Reactants Products
  12. 12. Mg + Cl2  2 MgCl B. 2 Ca + O2  2 CaO C. Zn + S  2 ZnS D. C + O2  2 CO Because atoms must be equal on each side of the equation: The correct answer is B A. Ca Ca O O O Ca Ca O
  13. 13. 2 Mg + 2 HCl → MgCl2 + H2      When the above equation is balanced, the coefficient for magnesium is — A 0 The correct B 1 answer is C C 2 D 4
  14. 14. Iron + Oxygen  Rust   100 g + ?g  143g What mass of oxygen is needed?43 g Oxygen Choice D