1. Chapter 4: Reactions in Aqueous Solution
Chemistry: McMurry and Fay, 6th Edition
Chapter 3: Mass Relationships in Chemical Reactions
2/23/2019 5:59:27 AM
Chapter 4: Reactions in Aqueous Solution
Copyright © 2011 Pearson Prentice Hall, Inc.

2. 4.1-4.2 Concentrations of Reactants in Solution: Molarity
Chapter 3: Formulas, Equations, and Moles
2/23/2019
Concentrations of Reactants in Solution: 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.
It’s the volume of solution that’s needed and not simply the volume of water (assuming water is the solvent). Either pictures or showing a volumetric flask might be helpful.

3. Concentrations of Reactants in Solution: Molarity
Chemistry: McMurry and Fay, 6th Edition
Chapter 3: Mass Relationships in Chemical Reactions
Concentrations of Reactants in Solution: Molarity
2/23/2019 5:59:27 AM
Copyright © 2011 Pearson Prentice Hall, Inc.

4. Concentrations of Reactants in Solution: Molarity
Chapter 3: Formulas, Equations, and Moles
2/23/2019
Concentrations of Reactants in Solution: Molarity
Molarity converts between mole of solute and liters of solution:
molarity =
moles of solute
liters of solution
1.00 mol of sodium chloride placed in enough water to make 1.00 L of solution would have a concentration equal to:
1.00 mol
mol
= 1.00
or 1.00 M
1.00 L L
Copyright © 2008 Pearson Prentice Hall, Inc.

5. Concentrations of Reactants in Solution: Molarity
Chapter 3: Formulas, Equations, and Moles
2/23/2019
Concentrations of Reactants in Solution: Molarity
What is the molarity of a solution made by dissolving 2.5 g of NaCl in enough water to make 125 ml of solution?
How many grams of solute would you use to prepare 1.50 L of M glucose, C6H12O6?
Calculate the volume of a 0.80M potassium bromide solution containing 23.6 g of potassium bromide.
Copyright © 2008 Pearson Prentice Hall, Inc.

6. Dilution

7. Diluting Concentrated Solutions
Chapter 3: Formulas, Equations, and Moles
2/23/2019
Diluting Concentrated Solutions
dilute solution
concentrated solution + solvent
initial
final
Mi Vi = Mf Vf Or
M1V1 = M2V2
Since the number of moles of solute remains constant, all that changes is the volume of solution by adding more solvent.
Copyright © 2008 Pearson Prentice Hall, Inc.

8. Diluting Concentrated Solutions
Chapter 3: Formulas, Equations, and Moles
2/23/2019
Diluting Concentrated Solutions
1. Sulfuric acid is normally purchased at a concentration of 18.0 M. How would you prepare mL of M aqueous H2SO4?
2. To what volume should you dilute L of a 15.0 M NaOH solution to obtain a 3.00 M NaOH solution?
Add acid to water!
Copyright © 2008 Pearson Prentice Hall, Inc.

9. 4.8-4.9 Solution Stoichiometry
Chapter 3: Formulas, Equations, and Moles
Solution Stoichiometry
2/23/2019
In aqueous reactions, quantities of reactants and products are often specified in terms of volume and concentrations.
We can use the stoichiometric coefficients in the chemical equation to convert to the amount of another reactants of products in moles.
aA + bB
cC + dD
Volume of
Solution of A
Moles of A
Moles of B
Volume of
Solution of B
These problems still come back to moles.
Molarity of A
Mole Ratio Between A and B (Coefficients)
Molarity
of B
Dang
Copyright © 2008 Pearson Prentice Hall, Inc.

10. Solution Stoichiometry
Chapter 3: Formulas, Equations, and Moles
Solution Stoichiometry
2/23/2019
What volume of M H2SO4 is needed to react with 50.0 mL of M NaOH?
H2SO4(aq) + 2NaOH(aq)
Na2SO4(aq) + 2H2O(l)
Volume of
Solution of NaOH
Moles of
NaOH
Moles of
H2SO4
Volume of
Solution of H2SO4
Molarity of NaOH
Molarity of H2SO4
Mole Ratio Between NaOH and H2SO4
Dang
Copyright © 2008 Pearson Prentice Hall, Inc.

11. Example
What volume of M KCl is required to completely react with L of M Pb(NO3)2 in the reaction
2 KCl(aq) + Pb(NO3)2(aq)  PbCl2(s) + 2 KNO3(aq)
Dang

12. Example
What is the minimum amount (L) of 6.0 M H2SO4 necessary to produce 25.0 g of H2 . Assumed H2SO4 is limited
2 Al(s) H2SO4(aq)  Al2(SO4)3(aq) H2(g)

13. Titration The base solution is the titrant in the burette.
As the base is added to
the acid, the H+ reacts with
the OH– to form water.
But there is still excess
acid present so the color
does not change.
At the titration’s endpoint,
just enough base has been
added to neutralize all the
acid. At this point the
indicator changes color.
Dang

14. Example
The titration of mL of HCl solution of unknown concentration requires mL of M NaOH solution to reach the end point. What is the concentration of the unknown HCl solution?
Dang

15. Examples
A mL sample of an unknown H3PO4 solution is titrated with a M NaOH. The equivalence point is reached when mL of NaOH solution is added. What is the concentration of the unknown H3PO4 solution? The neutralization reaction is
H3PO4(aq) NaOH(aq)  3H2O(l) + Na3PO4(aq)
Dang

16. Electrolytes and Nonelectrolytes
materials that dissolve in water to form a solution that will conduct electricity are called electrolytes
materials that dissolve in water to form a solution that will not conduct electricity are called nonelectrolytes

17. Electrolytes in Aqueous Solution
Chapter 4: Reactions in Aqueous Solution
2/23/2019
Electrolytes in Aqueous Solution
Strong Electrolytes: Compounds that dissociate to a large extent into ions when dissolved in water.
KCl(aq)
K1+(aq) + Cl1-(aq)
Weak Electrolytes: Compounds that dissociate to a small extent into ions when dissolved in water.
H1+(aq) + CH3CO21-(aq)
CH3CO2H(aq)
For a 0.10 M solution, KCl is approximately 98% dissociated while CH3CO2H (acetic acid) is a little more than 1% dissociated.
The size of the arrows indicate which side of the chemical equation the equilibrium lies on.
The use of the equilibrium arrows is minimal until later chapters on kinetics and chemical equilibrium.
Nonelectrolytes: Substances which do not produce ions in aqueous solutions.
H2O
C12H22O11(aq)
C12H22O11(s)
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18. Electrolytes in Aqueous Solution
Hydroxides are also ionic compounds.

19. Conceptual question
Three different substances, A2X, A2Y, and A2Z, are dissolved in water, with the following results. (Water molecules are omitted for clarity.)
(a) Which of the substances is the strongest electrolyte, and which is the weakest? Explain.
(b) What is the molar concentration of A ions and Y ions in a M solution of A2Y?
(c) What is the percent ionization of A2X indicated in the graphical representation?

20. Calculating the Concentration of Ions in a Solution
at is the total molar concentration of ions in a M solution of the strong electrolyte Na2SO4, assuming complete dissociation?
What is the molar concentration of Br– ions in a M aqueous solution of FeBr3, assuming complete dissociation?

21. Some Ways That Chemical Reactions Occur
Chapter 4: Reactions in Aqueous Solution
2/23/2019
Some Ways That Chemical Reactions Occur
Precipitation Reactions: Processes in which soluble reactants yield an insoluble solid product that falls out of solution.
NaNO3(aq) + AgCl(s)
AgNO3(aq) + NaCl(aq)
Copyright © 2008 Pearson Prentice Hall, Inc.

22. Some Ways That Chemical Reactions Occur
Acid-Base Neutralization Reactions: Processes in which an acid reacts with a base to yield water plus a salt.
H2O(l) + NaCl(aq)
HCl(aq) + NaOH(aq)
Acid Base  Water + Salt

23. Some Ways That Chemical Reactions Occur
Chapter 4: Reactions in Aqueous Solution
2/23/2019
Some Ways That Chemical Reactions Occur
Oxidation-Reduction (Redox) Reactions: Processes in which one or more electrons are transferred between reaction partners (atoms, molecules, or ions).
MgCl2(aq) + H2(g)
Mg(s) + 2HCl(aq)
Element + Compound  Compound + Element
Neutral state: (s), (l), (g)
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24. Precipitation Reactions and Solubility Guidelines
Write the chemical formulas of the products (use proper ionic rules).
CB + AD
AB + CD
double replacement reaction
*Remember that metal cation does not bond to another
metal cation

25. Aqueous Reactions and Net Ionic Equations
Chapter 4: Reactions in Aqueous Solution
2/23/2019
Aqueous Reactions and Net Ionic Equations
Molecular Equation: All substances in the chemical equation are written using their complete formulas as if they were molecules.
NaNO3(aq) + AgCl(s)
AgNO3(aq) + NaCl(aq)
strong electrolytes
indicated as (aq)
soluble
Precipitate
insoluble
Granted, all of the substances in the chemical equation are ionic compounds but it’s common to call this the molecular equation.
Pictures are useful especially with this reaction. Solutions of lead(II) nitrate and potassium iodide are colorless while the precipitate of lead(II) iodide is yellow.
Copyright © 2008 Pearson Prentice Hall, Inc.

26. Aqueous Reactions and Net Ionic Equations
Chapter 4: Reactions in Aqueous Solution
2/23/2019
Aqueous Reactions and Net Ionic Equations
Ionic Equation: All of the strong electrolytes are written as ions.
AgNO3(aq)
NaCl(aq)
Ag2+(aq) + NO31- (aq) + Na1+(aq) + Cl1-(aq)
Na1+(aq) + NO31- (aq) + AgCl(s)
Note the proper charges (as learned previously when writing ionic compound formulas).
NaNO3(aq)
Copyright © 2008 Pearson Prentice Hall, Inc.

27. Aqueous Reactions and Net Ionic Equations
Chapter 4: Reactions in Aqueous Solution
2/23/2019
Aqueous Reactions and Net Ionic Equations
Spectator Ions: Ions that undergo no change during the reaction and appear on both sides of the reaction arrow.
Ag2+(aq) + NO31- (aq) + Na1+(aq) + Cl1-(aq)
Na1+(aq) + NO31- (aq) + AgCl(s)
Copyright © 2008 Pearson Prentice Hall, Inc.

28. Aqueous Reactions and Net Ionic Equations
Chapter 4: Reactions in Aqueous Solution
2/23/2019
Aqueous Reactions and Net Ionic Equations
Net Ionic Equation: Only the ions undergoing change are shown.
AgCl2(s)
Ag+(aq) + Cl1-(aq)
This doesn’t suggest that you can actually have a solution of iodide ion. The corresponding cations and anions are present but they are spectator ions.
An aqueous solution that contains lead(II) ion when mixed with another one that contains iodide ion will typically produce a precipitate of lead(II) iodide.
Copyright © 2008 Pearson Prentice Hall, Inc.

30. Example
Write the molecular, ionic, and net ionic equations for the reaction that occurs when
aqueous solutions of PbCl2 and Na2SO4 are mixed

31. Example
Write the molecular, ionic, and net ionic equations for the reaction that occurs when
Aqueous solution of Mg(NO3)2 and NH4OH are mixed