John E. McMurry • Robert C. Fay

C H E M I S T R YSixth Edition

Chapter 3Mass Relationships in Chemical Reactions

These Sections Will NOT be on EXAM 1

Section 3.6 – 3.9

Concentrations of Reactants in Solution: MolarityMolarity: The number of moles

of a substance dissolved in each liter of solution.

Solution: A homogeneous mixture.

Solute: The dissolved substance in a solution.

Solvent: The major component in a solution

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:

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?

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

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?

aA + 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

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 ofH2SO4

Volume ofSolution of H2SO4

Moles ofNaOH

Volume ofSolution of NaOH

Mole Ratio Between H2SO4 and NaOH

Molarity of NaOH

Molarity of H2SO4

ExampleWhat is the minimum amount (L) of 6.0 M H2SO4

necessary to produce 25.0 g

Assumed H2SO4 is limited

2 Al(s) + 3 H2SO4(aq) Al2(SO4)3(aq) + 3 H2(g)

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.

unknown concentration solutionErlenmeyerflask

buretstandard solution(known concentration)

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

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

Concentrationof HCl

Mole Ratio Between NaOH and HCl

Volume of HCl

Molarity of NaOH

ExampleWhat 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)