Chapter 3 - Stoichiometry

# Chapter 3 - Stoichiometry - Chapter 3: Stoichiometry...

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1 Chapter 3: Stoichiometry Chapter 3: Stoichiometry Stoichiometry is the study of the quantitative relationships in substances and their reactions –Chemical equations –The mole and molar mass –Chemical formulas –Mass relationships in equations –Limiting reactant Chemical Equations Chemical Equations • A chemical equation is a shorthand notation to describe a chemical reaction – Just like a chemical formula, a chemical equation expresses quantitative relations • Subscripts tell the number of atoms of each element in a molecule • Coefficients tell the number of molecules

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2 Combination Reactions Combination Reactions •Examp les: N 2 ( g ) + 3 H 2 ( g ) ⎯⎯→ 2 NH 3 ( g ) C 3 H 6 ( g ) + Br 2 ( l ) ⎯⎯→ C 3 H 6 Br 2 ( l ) 2 Mg ( s ) + O 2 ( g ) ⎯⎯→ 2 MgO ( s ) Two or more substances react to form one product Chemical Equations Chemical Equations A chemical equation is a shorthand notation to describe a chemical reaction 2Mg + O 2 Ú 2MgO magnesium react to magnesium and oxygen form oxide
3 Anatomy of a Chemical Equation Anatomy of a Chemical Equation CH 4 ( g )+2O 2 ( g )C O 2 ( g )+2H 2 O( g ) Reactants appear on the left side of the equation. Products appear on the right side of the equation. The states of the reactants and products are written in parentheses to the right of each compound.

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4 Definitions Definitions Reactants are the substances consumed (i.e. magnesium and oxygen ) Products are the substances formed magnesium oxide Coefficients are numbers before the formula of a substance in an equation A balanced equation has the same number of atoms of each element on both sides of the equation Writing Balanced Equations Writing Balanced Equations Write the correct formula for each substance H 2 + Cl 2 HCl Add coefficients so the number of atoms of each element are the same on both sides of the equation H 2 + Cl 2 2 HCl H 2 atoms 2 atoms Cl 2 atoms 2 atoms
5 Balancing Chemical Equations Balancing Chemical Equations Assume one molecule of the most complicated substance C 5 H 12 + O 2 CO 2 + H 2 O Adjust the coefficient of CO 2 to balance C C 5 H 12 + O 2 5CO 2 + H 2 O Adjust the coefficient of H 2 O to balance H C 5 H 12 + O 2 5CO 2 + 6H 2 O Adjust the coefficient of O 2 to balance O C 5 H 12 + 8O 2 5CO 2 + 6H 2 O Check the balance by counting the number of atoms of each element. Balancing Equations Balancing Equations Sometimes fractional coefficients are obtained C 5 H 10 + O 2 CO 2 + H 2 O C 5 H 10 + O 2 5CO 2 + H 2 O C 5 H 10 + O 2 5CO 2 + 5H 2 O C 5 H 10 + (15/2)O 2 5CO 2 + 5H 2 O Multiply all coefficients by the denominator 2 C 5 H 10 + 15 O 2 10 CO 2 + 10 H 2 O

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## This note was uploaded on 05/09/2010 for the course CHEMISTRY 3150:153 taught by Professor Hu,jun during the Spring '10 term at Kent State.

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Chapter 3 - Stoichiometry - Chapter 3: Stoichiometry...

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