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Chapter 12 Stoichiometry. Like a Recipe. A balanced chemical equation provides the same kind of quantitative information that a recipe does. What is it??. Chemists use balanced chemical equations as a basis to calculate how much reactant is needed or product is formed in a reaction.
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Like a Recipe • A balanced chemical equation provides the same kind of quantitative information that a recipe does.
What is it?? • Chemists use balanced chemical equations as a basis to calculate how much reactant is needed or product is formed in a reaction. • The calculation of quantities in chemical reactions is a subject of chemistry called stoichiometry
Let’s Look at an everyday example! • In a five day work week, tiny tike is scheduled to make 640 tricycles. How many wheels should be in the plant on Monday morning to make those tricycles?
Interpreting Chemical Equations • A balanced chemical equation can be interpreted in terms of different quantities, including numbers of atoms, molecules, or moles; mass; and volume.
Interpreting (cont.) • Always remember : Mass and atoms are always conserved in a chemical reaction.
Writing and Using Mole Ratios • Mole Ratios are used to convert between: • moles of reactant and moles of product • moles of reactants • moles of products • A mole ratio is a conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles.
Example #1 • List the mole ratios present in the equation
Practice on your own • Page 360 #11
Practice on your Own • Page 361 # 13
Other Stoichiometric Calculations • In a typical stoichiometric problem, • given quantity is first converted to moles • mole ratio from the balanced equation is used to calculate the number of moles of the wanted substance • moles are converted to any other unit of measurement related to the unit mole, as the problem requires
Practice on your own • Page 364 # 15
Limiting Reagent and Excess Reagent • limiting reagent is the reagent that determines the amount of product that can be formed by a reaction • Excess Reagent- is the reagent not used up (what is left over in a chemical reaction)
Practice on your own • Page 370 # 25
Percent Yield • The percent yield is a measure of the efficiency of a reaction carried out in the laboratory. • Theoretical yield -maximum amount of product that could be formed from given amounts of reactants • Actual yield the amount of product that actually forms when the reaction is carried out in the laboratory
Practice on your own • Page 374-375 # 29 and 31