John E. McMurry • Robert C. Fay

C H E M I S T R YSixth Edition

Chapter 3Chapter 3Mass Relationships in Chemical Mass Relationships in Chemical ReactionsReactions

These Sections Will NOT be on EXAM 1

Concentrations of Reactants in Concentrations of Reactants in Solution: MolaritySolution: Molarity

Molarity: The number of moles of a substance dissolved in each liter of solution. In practice, a solution of known molarity is prepared by weighing an appropriate amount of solute, placing it in a container called a volumetric flask, and adding enough solvent until an accurately calibrated final volume is reached.

Solution: A homogeneous mixture.

Solute: The dissolved substance in a solution.

Solvent: The major component in a solution.

Concentrations of Reactants Concentrations of Reactants in Solution: Molarityin Solution: Molarity

Concentrations of Reactants in Concentrations of Reactants in Solution: MolaritySolution: Molarity

Molarity converts between mole of solute and liters of solution:

molarity =moles of solute

liters of solution

L

molor 1.00 M

1.00 L

1.00 mol= 1.00

1.00 mol of sodium chloride placed in enough water to make 1.00 L of solution would have a concentration equal to:

Concentrations of Reactants in Concentrations of Reactants in Solution: MolaritySolution: Molarity

How many grams of solute would you use to prepare 1.50 L of 0.250 M glucose, C6H12O6?

Calculate the volume of a 0.80M potassium bromide solution containing 23.6 g of potassium bromide.

What is the molarity of a solution made by dissolving 2.5 g of NaCl in enough water to make 125 ml of solution?

DilutionDilution

Diluting Concentrated SolutionsDiluting Concentrated Solutions

dilute solutionconcentrated solution + solvent

Mi Vi = Mf Vf

finalinitial

Since the number of moles of solute remains constant, all that changes is the volume of solution by adding more solvent.

OrM1V1 = M2V2

Diluting Concentrated SolutionsDiluting Concentrated Solutions

1. Sulfuric acid is normally purchased at a concentration of 18.0 M. How would you prepare 250.0 mL of 0.500 M aqueous H2SO4?

2. To what volume should you dilute 0.200 L of a 15.0 M NaOH solution to obtain a 3.00 M NaOH solution?

Solution StoichiometrySolution StoichiometryaA + bB cC + dD

Moles ofA

Volume ofSolution of A

Moles ofB

Volume ofSolution of B

Mole Ratio Between A and B (Coefficients)

Molar Mass of B

Molarity of A

Solution StoichiometrySolution Stoichiometry

H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l)

What volume of 0.250 M H2SO4 is needed to react with 50.0 mL of 0.100 M NaOH?

Moles ofNaOH

Volume ofSolution of NaOH

Moles ofH2SO4

Volume ofSolution of H2SO4

Mole Ratio Between NaOH and H2SO4

Molarity of NaOH

Molarity of NaOH

ExampleExample Nickel sulfate, NiSO4, reacts with sodium phosphate,

Na3PO4, to give a pale yellow-green precipitate of nickel phosphate, Ni3(PO4)3, and a solution of sodium sulfate, Na2SO4.

3NiSO4(aq) + 2 Na3PO4(aq) Ni3(PO4)3(s) + 3 Na2SO4(aq)

How many milliliters of 0.375M NiSO4 will react with 45.7

mL of 0.265 M Na3PO4?

TitrationTitration

How can you tell when the reaction is complete?

HCl(aq) + NaOH(aq) NaCl(aq) + 2H2O(l)

Titration: A procedure for determining the concentration of a solution by allowing a carefully measured volume to react with a solution of another substance (the standard solution) whose concentration is known.

Once the reaction is complete you can calculate the concentration of the unknown solution.

TitrationTitration

unknown concentration solutionErlenmeyerflask

buret standard solution(known concentration)

An indicator is added which changes color once the reaction is complete

TitrationTitration

HCl(aq) + NaOH(aq) NaCl(aq) + 2H2O(l)

48.6 mL of a 0.100 M NaOH solution is needed to react with 20.0 mL of an unknown HCl concentration. What is the concentration of the HCl solution?

Moles ofNaOH

Volume ofSolution of NaOH

Moles ofHCl

Volume ofSolution of HCl

Mole Ratio Between NaOH and HCl

Molarity of HCl

Molarity of NaOH

ExampleExample

What volume (in mL) of a 0.150 M HNO3 solution is required to completely react with 35.7 mL of a 0.108 M Na2CO3 solution according to the following balanced chemical equation?

Na2CO3(aq) + 2 HNO3(aq) 2 NaNO3(aq) + CO2(g) + H2O(l)