2. Chemical reactions and chemical equilibria 2011-students

2. Chemical reactions and chemical equilibria 2011-students...

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1 WONDERFUL WORLD OF CHEMISTRY! Chemistry 1311 Section E Welcome to the Professor Wendy Pell
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2 Chemistry 1301 / 1311 B PROFESSOR: Dr. Wendy G. Pell MCD 409 562-5800 x6041 wpell@uottawa.ca OFFICE HOURS: Mon. 4 – 5 pm Tues. 4 – 5 pm Wed. 4 – 5 pm Or by appointment
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3 Chemical Reactions and Chemical Equations A chemical reaction is a process by which a substance is changed into one or more new substances P 4 (s) + 6 Cl 2 (g) 4 PCl 3 (l)
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4 A chemical reaction is depicted using a chemical equation: P 4 (s) + 6 Cl 2 (g) 4 PCl 3 (l) reactants products arrow represents chemical reaction The numbers in front are called stoichiometric coefficients Letters (s), (l), (g), and (aq) represent physical states (solid, liquid, gas, and dissolved in water). Chemical Reactions and Chemical Equations
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5 Chemical Reactions and Chemical Equations This equation means: P 4 (s) + 6 Cl 2 (g) 4 PCl 3 (l) 1 mole of P 4 molecules in the solid state and 6 moles of chlorine in the gas state react to form 4 moles of phosphorus trichloride in the liquid state P 4 (s) + 6 Cl 2 (g) 4 PCl 3 (l)
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6 Balancing Chemical Equations Law of conservation of mass: mass is neither created nor destroyed. The same number and kind of atoms must be present before and after a chemical reaction. Before reaction 1 mole of C 2 moles of O 4 moles of H CH 4 + O 2 CO 2 + H 2 O After reaction 1 mole of C 3 moles of O 2 moles of H Overall: 1 mole O created and 2 moles H destroyed! VIOLATES law of conservation of mass! EQUATION IS NOT BALANCED
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7 Balancing Chemical Equations 2 2 Before reaction 1 mole of C 4 moles of O 4 moles of H After reaction 1 mole of C 4 moles of O 4 moles of H BALANCED! Practice balancing chemical equations! CH 4 + O 2 CO 2 + H 2 O (For now, you do not need to be able to predict products of reactions! Just balance the equations.)
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8 Chemical Reaction - Balancing Equations Nitrogen monoxide + oxygen nitrogen dioxide Step 1: Write the reaction using chemical symbols. Step 2: Balance the chemical equation.
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9 Balancing Equations Never introduce extraneous atoms to balance. Never change a formula for the purpose of balancing an equation.
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10 Balancing Equation Strategy Balance elements that occur in only one compound on each side first. Balance free elements last. Balance unchanged polyatomics as groups. Fractional coefficients are acceptable and can be cleared at the end by multiplication.
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11 Example 4-2 Writing and Balancing an Equation: The Combustion of a Carbon-Hydrogen-Oxygen Compound. Liquid triethylene glycol, C 6 H 14 O 4 , is used a a solvent and plasticizer for vinyl and polyurethane plastics. Write a balanced chemical equation for its complete combustion.
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12 2. Balance H. 4. Multiply by two Example 4-2 3. Balance O. and check all elements . Chemical Equation: 1. Balance C.
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13 STOICHIOMETRY STOICHIOMETRY The study of the quantitative aspects of chemical reactions The quantity of product formed from a reaction depends upon the amount of reactant available.
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14 Carbohydrates are compounds containing C, H and O in which the H to O ratio is 2:1. A 4.220 g sample of a carbohydrate is
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2. Chemical reactions and chemical equilibria 2011-students...

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