110_Fa11_LUZ-week5ST (1) - Week 5: Lectures 13 15 Chemical...

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Week 5: Lectures 13 – 15 Lecture 13: W 9/21 Lecture 14: F 9/23 Lecture 15: M 9/26 Reading: BLB Ch 2.6, 2.9, 3.3 – 3.5; 9.1 – 9.3 Homework: BLB 3:25, 29, 35, 37, 51, 53; Supp 3:1 – 9 BLB 9:23, 25, 27, 38; Sup 9:1 – 7 Reminder: ALEKS Objective 5 due on Tue, 9/27 “No Score” from Exam 1?? Not a problem—Go see Mike Joyce in 210 Whitmore or email him at mjj12@psu.edu Jensen Chem 110 Chap3 Page: 2 Chemical Formulas Molecular Formula: chemical formula with the total number of atoms and their relative proportions in each molecule. Empirical Formula: chemical formula with the smallest integer subscripts for a given molecule. Structural Formula: chemical formula with structural information about connectivity and angles .
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Jensen Chem 110 Chap3 Page: 3 Connecting microscopic (atoms) to macroscopic (weight) using Important Connections • Avogadro ! s number (N A ): Connects molecules (or atoms) to moles • Molar Mass (in g/mol) connects mass to moles; connects experimentally measured property to moles (or molecules) of substance; the molar mass (in g/mol) of any substance is always numerically equal to its formula weight (in amu). • Empirical Formula: chemical formula with the smallest integer subscripts; tells relative number of moles (molar ratio) of each element in a compound ; obtained from mass percent or molecular formula ; • Balanced chemical equation: connects moles (molecules) of reactants with moles (molecules) of products; related to conservation of mass • Conservation of mass and energy: mass of products = mass of reactants; energy is conserved but can change its form Jensen Chem 110 Chap3 Page: 4 Coefficients and Subscripts • In a molecule , subscripts denote the number of ________ per molecule or formula unit C 6 H 12 O 6 : one C 6 H 12 O 6 molecule has __ C, __ O, and __ H atoms. Mg(NO 3 ) 2 : one Mg(NO 3 ) 2 formula unit has __ Mg, __ N, and __ O atoms • In a reaction , coefficients denote the relative number of ________ of each compound 2 H 2 + O 2 ! 2 H 2 O ! Changing the subscripts changes the _________ of the molecule . ! Changing the coefficient changes the _________ of that molecule , not the identity .
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Jensen Chem 110 Chap3 Page: 5 Working with Formulas Example: How many moles of ammonium ions are present in 30.9 g of ammonium sulfate? A. 0.468 mol B. 0.288 mol C. 0.234 mol D. 2.14 mol E. 3.47 mol Jensen Chem 110 Chap3 Page: 6 Working with Formulas Practice Example: Which of the following has the greatest number of total atoms present? A. 6.022 x 10 23 O 2 molecules B. 0.1 mol C 6 H 12 O 6 C. 56 g Fe D. 0.4 mol CH 4 E. 4.4 g of H 2
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Jensen Chem 110 Chap3 Page: 7 Percent Composition: Mass Percent contributed by each element in compound (Note: percentage must add to 100) 1. Given chemical formula, % element = (# of element ) ( AW of element ) FW of compound " 100 Example: What is the mass percent of C in CO 2 ? C= _____ amu; O = _____ amu; CO
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This note was uploaded on 01/18/2012 for the course CHEM 110 taught by Professor Hofmann,brucerob during the Fall '08 term at Pennsylvania State University, University Park.

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110_Fa11_LUZ-week5ST (1) - Week 5: Lectures 13 15 Chemical...

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