BLBCJM-CH3-07

BLBCJM-CH3-07 - Stoichiometry: Calculations With Chemical...

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Unformatted text preview: Stoichiometry: Calculations With Chemical Formulas and Chapter 3 P2 Due Week of 9/24; 3.4, 3.12, 3.20, 3.24, 3.34, 3.46 3.58, 3.63, 3.73, 3.91 Chemical Stoichiometry • Stoichiometry - The study of quantities of materials consumed and produced in chemical reactions. • Lavoisier: mass is conserved in a chemical reaction. • Chemical equations: descriptions of chemical reactions. • Two parts to an equation: reactants and products: 2H 2 + O 2 → 2H 2 O Chemical Equations 3 ways of representing the reaction of H 2 with O 2 to form H 2 O A process in which one or more substances is changed into one or more new substances is a chemical reaction A chemical equation uses chemical symbols to show what happens during a chemical reaction reactants products How to “Read” Chemical Equations 2 Mg + O 2 2 MgO 2 atoms Mg + 1 molecule O 2 makes 2 formula units MgO 2 moles Mg + 1 mole O 2 makes 2 moles MgO 48.6 grams Mg + 32.0 grams O 2 makes 80.6 g MgO IS NOT 2 grams Mg + 1 gram O 2 makes 2 g MgO 2Na + 2H 2 O → 2NaOH + H 2 2K + 2H 2 O → 2KOH + H 2 • Stoichiometric coefficients: numbers in front of the chemical formulas; give ratio of reactants and products. Chemical Equations Chemical Equations Chemical Equations • Law of conservation of mass: matter cannot be lost in any chemical reactions. Balancing Chemical Equations Balancing Chemical Equations 1. Write the correct formula(s) for the reactants on the left side and the correct formula(s) for the product(s) on the right side of the equation. Ethane reacts with oxygen to form carbon dioxide and water C 2 H 6 + O 2 CO 2 + H 2 O 1. Change the numbers in front of the formulas ( coefficients ) to make the number of atoms of each element the same on both sides of the equation. Do not change the subscripts. 2C 2 H 6 NOT C 4 H 12 Balancing Chemical Equations 1. Start by balancing those elements that appear in only one reactant and one product. C 2 H 6 + O 2 → CO 2 + H 2 O C 2 H 6 + O 2 → 2CO 2 + 3H 2 O 1. Balance those elements that appear in two or more reactants or products. Check C 2 H 6 + 3.5O 2 → 2CO 2 + 3H 2 O 2C 2 H 6 + 7O 2 → 4CO 2 + 6H 2 O xercise 3.2: Balance the following equations by providing the missing coefficients. ) Fe(s) + O 2 (g) → Fe 2 O 3 (s) ) C 2 H 4 (g) + O 2 (g) → CO 2 (g) + H 2 O(g) ) Al(s) + HCl(aq) → AlCl (aq) + H (g) • Combination reactions have fewer products than reactants: 2Mg( s ) + O 2 ( g ) → 2MgO( s ) The Mg has combined with O 2 to form MgO. • Decomposition reactions have fewer reactants than products: 2NaN 3 ( s ) → 2Na( s ) + 3N 2 ( g ) (the reaction that occurs in an air bag) Some Simple Patterns of Chemical Reactivity Combination and Decomposition Reactions Combination and Decomposition Reactions Combustion in Air Some Simple Patterns of Some Simple Patterns of Chemical Reactivity Chemical Reactivity Combustion is the burning of a substance in oxygen from air: C 3 H 8 ( g ) + 5O 2 ( g ) → 3CO 2 ( g ) + 4H 2 O( l ) Molecular mass (or molecular or formula weight) is...
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This note was uploaded on 08/17/2008 for the course CHE 101 taught by Professor Churchhill during the Spring '08 term at SUNY Buffalo.

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BLBCJM-CH3-07 - Stoichiometry: Calculations With Chemical...

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