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Published byIlona Říhová Modified over 5 years ago
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Ch 9 Stoichiometry How does this apply to everyday life?
Following recipe for cooking/ baking Following directions in building/construction Knowing how much of ingredients needed Using Balanced Chem Eqns Knowing how much reagent(s) needed to make product or how much product formed in reaction Stoichiometry: “element” and “to measure” = calculation of amounts of substances involved in chem rxn
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9.1 Intro 4 Types of Problems Mole Ratios Remember Molar Mass
mol given moles of unknown moles given mass of unknown mass given moles of unknown mass given mass of unknown Mole Ratios Written as conversion factors Remember Molar Mass Mass (g) of 1 mol of substance
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9.2 Ideal Stoichiometric Calculations
Don’t Forget Mass Conservation! (Mass and atoms conserved; reactants = products) Given quantity x conversion factor = unknown quantity Type 1: mole-to-mole conversion Type 2: mole-to-gram conversion Type 3: gram-to-mole conversion Type 4: mass-to-mass conversion
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Arithmetic of Equations
Interpreting Chem Eqns Quantities of atoms: # and type of atoms in reactant(s) and product(s) Quantities of molecules: # and type of molecules in reactant(s) and product(s) Quantities of moles: coefficients of balanced ch rxn is # moles of reactants/ products! Mass: follows law of conservation of mass; use mole relationships Volume: remember 1 mole of gas at STP has volume of 22.4L; coefficients to know relative volumes
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Chem Calculations Moles ratios used? Steps in Stoichiometric problems
Mole ratios are the coefficients in a balanced chemical equation! Relates reactants to products Steps in Stoichiometric problems Get moles: Convert given quantity to moles Mole Ratio: Use mole ratio from equations to find moles of wanted component Get Right Units: Convert moles of wanted to desired unit
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9.3Limiting Reagent and Percent Yield
Limiting Reagents: insufficient quantity, run out reaction is over/ limit product made Excess Reagents: not completely used up/ have extra when reaction is over
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Yield Theoretical yield: max amount of product that could be formed from all reactants Actual Yield: amount actually formed in exp. Percent yield = actual yield/ theoretical yield x100% Measures efficiency of exp; remember % error
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