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r: 100 Chapter Three Stoichiometry Last, we balance the oxygen atoms. Note that the right side of the preceding equation tains seven oxygen atoms, whereas the left side has only three. We can correct thi putting a 3 before the O 2 to produce the balanced equation: C 2 H s OH(l) + 30 2 (g) -7 2C0 2 (g) + 3H 2 0(g) 10 60 (2 x 2)0 30 70 70 Now we check: C 2 H s OH(l) + 30 2 (g) -7 2C0 2 (g) + 3H 2 0(g) 2 C atoms 2 C atoms 6 H atoms 6 H atoms 70 atoms 70 atoms The equation is balanced. The balanced equation can be represented as follows: + + You can see that all the elements balance. PROBLEM-SOLVING STRATEGY Writing and Balancing the Equation for a Chemical Reaction 1 ~ Determine what reaction is occurring. What are the reactants, the products, and the physical states involved? 2 ~ Write the unbalanced equation that summarizes the reaction described in step 1. 3 ~ Balance the equation by inspection, starting with the most complicated molecule(s). Determine what coefficients are necessary so that the same number of each type of atom appears on both reactant and product sides. Do not change the identities
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Unformatted text preview: or products. EXAMPLE 3.13 __ Chromate and dichromate compounds are carcinogens (cancer-inducing agents) and should be handled very carefully. Chromium compounds exhibit a variety of bright colors. When solid ammonium dichro-mate, (NH4)2Cr207, a vivid orange compound, is ignited, a spectacular reaction occurs, as shown in the two photographs on the next page. Although the reaction is actually somewhat more complex, let's assume here that the products are solid chromium(III) oxide, nitrogen gas (consisting of N2 molecules), and water vapor. Balance the equation for this reaction. Solution 1 ~ From the description given, the reactant is solid ammonium dichromate, (NH4)2Cr207(S), and the products are nitrogen gas, N 2 (g), water vapor, H 2 0(g), and solid chromium(III) oxide, Cr203(S). The formula for chromium(III) oxide can be determined by recognizing...
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