Chapter 7 Chemistry Notes

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Unformatted text preview: ded after the arrow (including physical state) To conserve mass, the number of atoms of each type on the reactant side must exactly equal the atoms of each type on the product side. This is called balancing the chemical reaction. Balancing a Chemical Equation 1. 2. 3. 4. 5. Write the unbalanced Balance the following: equation with all chemical formulas written correctly. CoCl2 + Na3PO4 Co3(PO4)2 + NaCl Start with the most complex formula a. First balance elements that occur in only one other species. b. Usually metals before nonmetals. c. Continue until all elements are balanced. Change coefficients to smallest integer ratio. Specify state Check work. http://www.youtube.com/watch?v=vcsgc3hh1Ro 1 9/27/2013 Balancing a Chemical Equation 1. 2. 3. 4. 5. Write chemical formulas correctly. Start a. Elements that occur in only one other species. b. Usually metals first c. Continue to set coefficients until balanced. Balance the following: Al + Br2 AlBr3 Check for smallest integer ratio. Specify state Check work. Balancing a Chemical Equation 1. 2. 3. 4. 5. Write chemical formulas correctly. Start a. Elements that occur in only one other species. b. Usually metals first c. Continue to set coefficients until balanced. Balance the following: C3H6O + O2 CO2 + H2O Check for smallest integer ratio. Specify state Check work. http://www.youtube.com/watch?v=uCwHzTsx5yY&feature=player_embedded Example Balance Chemical Equations Example Balance Chemical Equations If you eat sugar (sucrose, C12H22O11) and breath oxygen (O2) your body produces, CO2 , H2O, and energy as products of the reaction: C12H22O11 + O2 CO2 + H2O + energy Bluing is a process of protecting steel from corrosion by creating a thin protective coating of magnetite (Fe3O4, blueblack). Magnetite adheres well to steel, in contrast hematite (Fe2O3, reddish) tends to flake off leading to corrosion. Fe2O3 + Δ Fe ! → ! Fe3O4 Answer: C12H22O11 (s) + 12 O2(g) 12 CO2(g) + 11 H2O(ℓ) Compare and Contrast the Results The two solutions (sugar vs salt) differ in their electrical conductivity. Evidence of Mobile Ions Molecular Ionic Substances that dissolve to form conductive solutions are called electrolytes. These solutions contain dissolved cations and anions. Substances that dissolve to form non-conductive solutions are called nonelectrolytes. These solutions contain neutral molecules. [A third category exists called weak electrolytes. Substances such as weak acid only partially dissociate into ions and therefore the solutions only conduct electricity poorly.] http://www.chem.iastate.edu/group/Greenbowe/sections/ projectfolder/flashfiles/thermochem/solutionSalt.swf When a salt dissolves it dissociates to form ions that can transport charge. 2 9/27/2013 Salts and Aqueous Solutions When you add salt (NaCl) to water- it dissolves to form ions as evidenced by the observation that a solution can conduct electricity (an electrolyte). We write: O NaCl(s) !H 2!→ Na+(aq) + Cl-(aq) or ! O NaCl(s) !H 2!→ NaCl(aq) (means sa...
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This note was uploaded on 02/04/2014 for the course CHEM 004:007 taught by Professor Russellarsen during the Fall '13 term at University of Iowa.

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