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Balancing Equations:

Balancing Equations:. Chemical and Nuclear. Ca. O. O. H. H. How molecules are symbolized. Cl 2 2Cl 2Cl 2. Molecules may also have brackets to indicate numbers of atoms. E.g. Ca(OH) 2. Notice that the OH is a group The 2 refers to both H and O

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Balancing Equations:

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  1. Balancing Equations: Chemical and Nuclear

  2. Ca O O H H How molecules are symbolized Cl2 2Cl 2Cl2 • Molecules may also have brackets to indicate numbers of atoms. E.g. Ca(OH)2 • Notice that the OH is a group • The 2 refers to both H and O • How many of each atom are in the following? a) NaOH b) Ca(OH)2 c) 3Ca(OH)2 Na = 1, O = 1, H = 1 Ca = 1, O = 2, H = 2 Ca = 3, O = 6, H = 6

  3. Mg Mg O O O  + Balancing equations: MgO Dalton: chemical reactions are the result of a rearrangement of atoms. Lavoisier: Conservation of Mass – “What goes in must come out” Number and types of atoms must be conserved. Thus, the number of a particular atom is the same on both sides of a chemical equation • Example: Magnesium + Oxygen Mg + O2 MgO • However, this is not balanced • Left: Mg = 1, O = 2 • Right: Mg = 1, O = 1

  4. Representing Reactions Word Equation: Magnesium + hydrochloric acid  magnesium chloride + hydrogen Skeleton Equation: Mg (s) + HCl (aq)  H2 (g) + MgCl2 (aq) When going from word equations to skeleton equations, don’t forget about HOBrFINCl gases!

  5. Balancing Equation Guidelines: • Balance the element with the greatest number of atoms (not H or O!) • Balance other elements in compounds. If an element is uncombined, usually leave it until last. • Balance H or O, if they are combined in compounds • Balance uncombined elements • Check

  6. 5 a) P4 + O2 P4O10 b) Li + H2O  H2+ LiOH c) Bi(NO3)3 + K2S Bi2S3 + KNO3 d) C2H6 + O2 CO2 + H2O 2 2 2 2 3 6 3.5 2 3 C2H6 + O2 CO2 + H2O 2 7 4 6

  7. Balance these skeleton equations: a) Mg + HCl  MgCl2 + H2 b) Ca + N2 Ca3N2 c) NH4NO3 N2O + H2O d) BiCl3 + H2S  Bi2S3 + HCl e) C4H10 + O2 CO2 + H2O f) O2 + C6H12O6 CO2 + H2O g) NO2 + H2O  HNO3 + NO h) Cr2(SO4)3+ NaOH  Cr(OH)3+ Na2SO4 • Al4C3 + H2O  CH4 + Al(OH)3

  8. Balance these skeleton equations: a) Mg + 2HCl  MgCl2 + H2 b) 3Ca + N2 Ca3N2 c) NH4NO3 N2O + 2H2O d) 2BiCl3 + 3H2S  Bi2S3 + 6HCl e) 2C4H10 + 13O28CO2 + 10H2O f) 6O2 + C6H12O66CO2 + 6H2O g) 3NO2 + H2O 2HNO3 + NO h) Cr2(SO4)3+ 6NaOH  2Cr(OH)3+ 3Na2SO4 i) Al4C3 + 12H2O 3CH4 + 4Al(OH)3

  9. Returning to reaction types • We have looked at several types of reactions without worrying about balancing • However, all equations should be balanced • Predict the products and balance these: (recall, metals above replace metals below, reactionswithwateryieldmetalhydroxides) Cu + Fe2(SO4)3 2 3 3 Fe + CuSO4  Ni + NaCl  NR (no reaction) 2 3 3 2 Al + CuCl2  Cu + AlCl3 Zn + Li2CO3 Li + ZnCO3  2 2 2 2 ½ LiOH + H2 Li + H2O  Al + O2  4 3 2 Al2O3

  10. Here are some more to complete & balance: a) KNO3 b) Pb(NO3)2 c) P4 + I2 • MgO + H3PO4 • Br2 + KI  f) Ca(OH)2 + HNO3 g) Bi2O3 + H2 h) Fe + O2 i) CaO + C 

  11. Here are some more to balance: a) 2KNO32KNO2 + O2 b) 2Pb(NO3)22PbO + 4NO2 + O2 c) P4 + 6I24PI3 d) 3MgO + 2H3PO4 Mg3(PO4)2 + 3H2O e) Br2 + 2KI  I2 + 2KBr f) Ca(OH)2 + 2HNO3 Ca(NO3)2 + 2H2O g) Bi2O3 + 3H22Bi + 3H2O h) 3Fe + 2O2 Fe3O4 i) 2CaO + 5C 2CaC2 + CO2

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