Chemistry Exam 3 Review Empirical Formula simplest whole number ration Steps 1 mass gives the number of grams of a particular element per 100 grams of compound Base the calculation on 100 grams of compound Each represents the mass in grams of that element 2 Determine the number of moles of each atom present in 100 grams of compound using the atomic masses of the elements present 3 Divide each value of the number of moles by the smallest of the values If the resulting number is a whole number these values represent the subscripts of the elements in the empirical formula 4 If the numbers obtained in the previous step are NOT whole numbers multiply each number by an integer so that the results are whole numbers Molecular formula exact formula of a molecule Steps 1 Obtain the empirical formula 2 Calculate the mass corresponding to the empirical formula 3 Calculate the ratio of the true molar mass to the empirical formula mass 4 The integer from the previous step represents the number of empirical formula units in 1 molecule When the empirical formula subscripts are multiplied by this integer the molecular formula results Percent Yield Actual yield Theoretical Yield x100 Reaction Types Combustion Fuel O2 g yields CO2 g H2O g Precipitation Reaction in which an insoluble substance forms and separates from the solution Acid Base neutralization acid base yields salt water Redox electrons are transferred from 1 material to another Decomposition Reactant breaks down into multiple products Solubility rules 1 NO3 soluble 2 Group 1 cations and NH4 soluble 3 Cl Br I soluble but not with Ag Hg2 2 Pb 2 4 SO4 2 soluble except with Ag Hg2 2 Pb 2 Ca 2 Ba 2 Sr 2 5 OH insoluble except with group 1 and NH4 6 S 2 CO3 2 PO4 3 insoluble except with group 1 and NH4 Complete Molecular Equation example Fe NO3 3 aq 3NaOH aq yields Fe OH 3 s 3NaNO3 aq Complete Ionic Equation example Fe 3 aq 3NO3 aq 3Na aq OH aq yields Fe OH 3 s 3Na aq 3NO3 aq Net Ionic Equation Fe 3 aq 3OH aq yields Fe OH 3 s Spectator ions ions which look the same on both sides of the equation not involved in the reaction Strong Acids to Know HI hydroiodic acid HClO4 perchloric acid H2SO4 sulfuric acid HBr hydrobromic acid HCl hydrochloric acid HNO3 nitric acid Weak Acids to Know H3PO4 phosphoric acid HF hydrofluoric acid CH3CO2H acetic acid Strong Bases to Know NaOH sodium hydroxide KOH potassium hydroxide Ba OH 2 barium hydroxide Ca OH 2 Calcium hydroxide Weak Bases to Know NH3 ammonia Arrhenius concept of acids and bases Acid produces H in an aqueous solution Base produces hydroxide ions in an aqueous solution Bronsted Lowry concept of acids and bases Acid proton donor Base proton acceptor pH log H3O or log H pH pOH 14 Sigfigs in H3O number of places after the decimal point in pH or pOH i e log 100 1 000 pH Dilution process of adding solvent to lower the concentration of solute in a solution Moles of solute before dilution moles of solute after dilution M1V1 M2V2
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