Stoichiometry StoichiometryStoichiometry includes all the
quantitative relationships involving:atomic and formula
masseschemical formulas. Mole ratio is a central conversion
factor.
Quantitative relationships among chemical formulas and chemical
equations.Mole concept can be used to calculate the relative
quantities of reactants and products in a chemical
rxs.2ExampleRelating the Numbers of Moles of Reactant and
Product
How many moles of AlCl3 are formed by the reaction of 1.5 mol of
Al in an excess of Cl2?Use the stoichiometric factor or mole ratio
in an equation:Write the Chemical Equation: Al (s) + Cl2
AlCl3Balance the Chemical Equation: 2 Al (s) + 3 Cl2 2AlCl3
3 ExampleUse the stoichiometric factor or mole ratio in an
equation:4 Stoichiometry (Limiting Reactant)The reactant that is
completely consumed determines the amount of product formed.
Anlogous sitution occurs in chemical rxns when one of the
reactants is used up before the others. The reaction stops as soon
as any one o the reactant is totally consumed, leaving the excess
reactants as leftovers.5 Example Consider the following
net-reaction:Determining the Limiting Reactant and amount of
Product formed in a Reaction. Anlogous sitution occurs in chemical
rxns when one of the reactants is used up before the others. The
reaction stops as soon as any one o the reactant is totally
consumed, leaving the excess reactants as leftovers.6 Stoichiometry
in Solutions Molarity (M) = Volume of solution (L) Amount of solute
(mol solute) If 0.440 mol of urea is dissolved in enough water to
make 1.000 L of solution the concentration is:curea = 1.000 L0.440
mol urea= 0.440 M CO(NH2)2
Molarity most widely used to quantify concentrationM=the number
of moles of solute in a liter of solutionExpress concentrations of
solutions quantitatively7 ExampleVolume moles massmolLg
molSOLUTION:8 Stoichiometry in SolutionsSolution Dilution
(Initial Molarity)(initial volume) = (final molarity)(final
volume)Mi Vi = ni = nf = Mf VfDilution- process of addition of
water to lower the concentration of a certain solutionWhen a
solvent is added to dilute a solution, the number of moles of
solute remains unchangedInitial Molarity > final molarityFinal
volume>initial volume9 ExampleSOLUTION:Vi =VfMfMiMi Vi = Mf
Vf
