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Balancing Chemical Reactions

Balancing Chemical Reactions. Balancing . Chemical reactions obey the law of conservation of matter which states that matter is neither created nor destroyed, it only changes forms (becomes rearranged )

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Balancing Chemical Reactions

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  1. Balancing Chemical Reactions

  2. Balancing • Chemical reactions obey the law of conservation of matter which states that matter is neither created nor destroyed, it only changes forms (becomes rearranged) • the number of atoms on the reactant side must equal the number of atoms on the product side Reactants  products

  3. Reactants Products Mg + 2HCl  MgCl2 + H2 Mass before = mass after (Law of conservation of matter) If the masses before and after are not equal, one of the compounds is in excess and the other is the limiting reagent.

  4. Rules for Balancing Equations 1. Determine the correct formula for reactants and products don’t forget diatomic molecules H2N2 O2 F2 Cl2 Br2I2 and polyatomic molecules (more than two) P4S8 2. Count the # of atoms of each element in the reactants and products 3. Balance each atom using coefficients. Never balance an equation by changing the subscripts 4. Check each atom to be sure that the equation is balanced.

  5. Helpful hints: • All elements have a charge of zero when uncombined. (no ionic charge) • Leave H and O until the end • If stuck, go back to the beginning and put a 2 in front of the most complex chemical

  6. Examples 1. Aluminum reacts with lead(II) hydroxide to produce aluminum hydroxide and lead.

  7. Examples 1. Aluminum reacts with lead(II) hydroxide to produce aluminum hydroxide and lead. Al + Pb(OH)2  Al(OH)3 + Pb

  8. Examples 1. Aluminum reacts with lead(II) hydroxide to produce aluminum hydroxide and lead. 2Al + 3Pb(OH)2  2Al(OH)3 + 3Pb

  9. Examples 2. Sulfur plus oxygen yield sulfur dioxide

  10. Examples 2. Sulfur plus oxygen yield sulfur dioxide S8 + O2  SO2

  11. Examples 2. Sulfur plus oxygen yield sulfur dioxide S8 + 8O2  8SO2

  12. Examples 3. Sodium sulfate and calcium borate react to make sodium borate and calcium sulfate.

  13. Examples 3. Lithium sulfate and calcium borate react to make lithium borate and calcium sulfate. Li2SO4 + Ca3(BO3 )2 Li3BO3 + CaSO4

  14. Examples 3. Lithium sulfate and calcium borate react to make lithium borate and calcium sulfate. 3Li2SO4 + Ca3(BO3)2 2Li3BO3 + 3CaSO4

  15. Examples 4. Diphosphorus trioxide combines with water to create phosphorous acid.

  16. Examples 4. Diphosphorus trioxide combines with water to create phosphorous acid. P2O3 + H2O  H3PO3

  17. Examples 4. Diphosphorus trioxide combines with water to create phosphorous acid. P2O3+ 3H2O  2H3PO3

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