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Counting Atoms and Balancing Chemical Equations

Counting Atoms and Balancing Chemical Equations. Subscripts. C 12 H 22 O 11 There are 12 atoms of Carbon There are 22 atoms of Hydrogen There are 11 atoms of Oxygen If there is not a subscript listed, it is understood to be 1. NaCl There is one atom of Sodium There is one atom of Chlorine.

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Counting Atoms and Balancing Chemical Equations

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  1. Counting Atoms and Balancing Chemical Equations

  2. Subscripts C12H22O11 There are 12 atoms of Carbon There are 22 atoms of Hydrogen There are 11 atoms of Oxygen If there is not a subscript listed, it is understood to be 1. NaCl There is one atom of Sodium There is one atom of Chlorine

  3. NaHCO3 Sodium – 1 Hydrogen – 1 Carbon – 1 Oxygen -3 HCl Hydrogen – 1 Chlorine - 1 Learning Check

  4. There are times you will see a compound with parenthesis. Pb(NO3)2 The 2 after the parenthesis indicates there are two sets of the parenthesis. Pb(NO3) (NO3) So, in counting the atoms, you would have the following: Lead – 1 Oxygen – 6 Nitrogen -2

  5. (NH4)3PO4 Nitrogen – 3 Hydrogen – 12 Phosphorus – 1 Oxygen – 4 Mg(OH)2 Magnesium – 1 Oxygen – 2 Hydrogen – 2 Learning Check

  6. Coefficient 2H2SO4 This means there are 2 compounds of sulfuric acid. Think: H2SO4 + H2SO4 Counting the atoms: Hydrogen – 4 Sulfur – 2 Oxygen – 8 Coefficient

  7. 3H3PO4 Hydrogen – 9 Phosphorus – 3 Oxygen - 12 2H2O Hydrogen – 4 Oxygen - 2 Learning Check

  8. Reading Chemical Equations The mass of all the reactants (the substances going into a reaction) must equal the mass of the products (the substances produced by the reaction). CH4 + 2O2 → CO2 + 2 H2O Reactants Products

  9. Law of Conservation of Mass In a chemical reaction, matter cannot be created or destroyed. It can only be changed. The reactants MUST contain the same elements and the same number of each element as the product. They CAN be in different compounds.

  10. Learning Check Do the following equations follow the law of conservation of mass? H2 + O2 H2O Na + O2 Na2O Mg + 2HCl MgCl2 + H2 HgO Hg + O2 N2 + 3H2 2NH3 2Na + 2H2O 2NaOH + H2 Zn + 2HCl ZnCl2 + H2 NO NO YES NO YES YES YES

  11. Balancing Equations Na + O2 → Na2O For this equation to be balanced, there must be equal amountsof Na in the reactants and products. You must add coefficients to balance this equation: 2Na + O2 → Na2O

  12. Balancing Equations Two ways… M. I. N. O. H. or Number charts

  13. Balancing Equations Two ways… M. I. N. O. H.

  14. Balancing Equations Two ways… Number charts

  15. Balancing Equations __H2 + __O2 __H2O 2 2 O - H - O - H - 2 2 4 1 2 2 4

  16. Balancing Equations __H2SO4 + __NaOH __H2O +__Na2SO4 2 2 Na - SO4 – O – H - 1 1 1 3 2 2 4 2 4 2 1 1 2 Na - SO4 – O – H -

  17. Balancing Equations __C3H8 + __O2 __CO2 +__H2O 5 3 4 C - O – H – 3 2 8 10 1 3 2 C - O – H – 3 7 10 8

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