c101-lecture-4 - Chemical Equations A chemical equationjust...

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1/31/11 1 Chemical Equations A chemical equation—just like a mathematical equation—is a way to express, in symbolic form, the reactions occurring in a chemical system. Balancing chemical equations Reaction stoichiometry Reagents limiting the extent of reaction Acid-base reactions Oxidation states of reactants and products Types of Chemical Reactions Combination Reactions: Atoms or molecules combine to form a new molecule 2H 2 + O 2 2H 2 O ClO + NO 2 ClNO 3 ClO + ClO ClOOCl Types of Chemical Reactions Decomposition Reactions: A molecule breaks apart to form different molecules or atoms NO 2 + sunlight O + NO 2C 7 H 5 (NO 2 ) 3 + heat 7CO(g) + 7C + 5H 2 O(g) + 3N 2 (g) Types of Chemical Reactions Displacement Reactions: An atom or molecule displaces an atom or molecule in the reaction partner H + Cl 2 HCl + Cl 2Na(s) + 2H 2 O( ± ) 2NaOH(aq) + H 2 (g) Types of Chemical Reactions Exchange Reactions: The components of two compounds are exchanged BaCl 2 (aq) + Na 2 SO 4 (aq) BaSO 4 (s) + 2NaCl(aq) 3NaOH(aq) + H 3 PO 4 (aq) Na 3 PO 4 (aq) + 3H 2 O( ± ) Balancing Chemical Equations Remember Conservation of Mass rule— matter is neither created nor destroyed in a chemical reaction. A balanced chemical equation must have the same number of each type of atom on the reactant side as on the product side.
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1/31/11 2 Balancing Chemical Equations Process for balancing chemical equations: 1. Determine correct chemical formulas of all reactants and products 2. Start with heavier atoms—balance number of these on reactant and product sides of equation 3. If elements appear in equation as either reactants or products, balance these last 4. Electrical charge must be balanced Balanced Chemical Equations Examples Write a balanced chemical equation for the reaction of Fe with oxygen to form iron(III) oxide 1. Fe + O 2 Fe 2 O 3 2. 2 Fe + O 2 Fe 2 O 3 Fe is currently balanced 3. 2 Fe + 3/2 O 2 Fe 2 O 3 O is now balanced coefficients must usually be integer numbers— multiply everything by 2 to remove 3/2 denominator: 4 Fe + 3 O 2 2 Fe 2 O 3 Balanced Chemical Equations Examples Write a balanced chemical equation for the combustion of methane—combustion is reaction with oxygen producing a flame. Complete combustion produces only CO 2 and H 2 O. Balanced Chemical Equations
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This note was uploaded on 03/05/2011 for the course CHEM 101 taught by Professor Scottnickolaisen during the Spring '11 term at California State University Los Angeles .

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c101-lecture-4 - Chemical Equations A chemical equationjust...

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