1. Chapter 4 Reactions in Aqueous Solution

2. A solution is a homogenous mixture of 2 or more substances
The solute is(are) the substance(s) present in the smaller amount(s)
The solvent is the substance present in the larger amount
Water is always the solvent (96% H2SO4)
Solution
Solvent
Solute
Soft drink (l)
H2O
Sugar, CO2
Air (g) N2
O2, Ar, CH4
Soft Solder (s) Pb Sn

3. Dissociation
When an ionic substance dissolves in water, the solvent pulls the individual ions from the crystal and solvates them.
This process is called dissociation.

4. Water’s power as an ionizing solvent results from the distribution of its electrons and its overall shape.
A polar molecule is one that has a + end and a - end. Water is one of the most polar molecules. d+ d-
H2O

5. Solvation is the process in which an ion is surrounded by solvent molecules arranged in a specific manner.
Hydration is the process in which an ion is surrounded by water molecules arranged in a specific manner. d+ d-
H2O

6. An electrolyte is a substance that, when dissolved in water forms ions, and hence, results in a solution that can conduct electricity.
A nonelectrolyte is a substance that, when dissolved does not form ions, and hence, results in a solution that does not conduct electricity.

7. Electrolytes
A strong electrolyte dissociates completely when dissolved in water.
A weak electrolyte only dissociates partially when dissolved in water.
Strong Electrolyte – 100% dissociation
NaCl (s) Na+ (aq) + Cl- (aq)
H2O
CH3COOH CH3COO- (aq) + H+ (aq)
Reversible reaction - Chemical equilibrium

8. Strong Electrolytes Are…
Strong acids:
HCl, HBr, HI, HNO3, HClO4, HClO3, H2SO4
Strong bases:
Group 1A metal hydroxide
[LiOH, KOH, NaOH, RbOH, CsOH]
Heavy group 2A metal hydroxides
[Ca(OH)2, Sr(OH)2, Ba(OH)2]

9. Acids HCl + NaOH = NaCl + H2O base Acid Gives OH- Gives H+ Arrhenius
Accepts H+
Lowry- Brønsted
Gives electrons
Accepts electrons
Lewis

10. Acids Hydrochloric (HCl) Hydrobromic (HBr) Hydroiodic (HI)
There are only seven strong acids:
Hydrochloric (HCl)
Hydrobromic (HBr)
Hydroiodic (HI)
Nitric (HNO3)
Sulfuric (H2SO4)
Chloric (HClO3)
Perchloric (HClO4)

11. Acids that ionize to form one H+ ion are called monoprotic acids
Acids that ionize to form one H+ ion are called monoprotic acids. Common monoprotic acids include HCl, HNO3 and HC2H3O2. Acids that ionize to form two H+ ions are called diprotic acids. A common diprotic acid is H2SO4.

12. Bases
Arrhenius defined bases as substances that increase the concentration of OH− when dissolved in water.
Brønsted and Lowry defined them as proton acceptors.

13. Common bases are NaOH, KOH, and Ca(OH)2
Common bases are NaOH, KOH, and Ca(OH)2. Compounds that do not contain OH– ions can also be bases. Proton transfer to NH3 (a weak base) from water (a weak acid) is an example of an acid–base reaction. Since there is a mixture of NH3, H2O, NH4+, and OH– in solution, We write: NH3(aq) + H2O(l)  NH4+(aq) + OH–(aq)

14. Strong and Weak Acids and Bases
• Strong acids and strong bases are strong electrolytes.
• They are completely ionized in solution.
• Strong bases include: Group 1A metal hydroxides, Ca(OH)2, Ba(OH)2, and Sr(OH)2.
• Strong acids include: HCl, HBr, HI, HClO3, HClO4, H2SO4, and HNO3.
• We write the ionization of HCl as:
HCl  H+ + Cl–
• Weak acids and weak bases are weak electrolytes.
• They are partially ionized in aqueous solution.
• HF(aq) is a weak acid; most acids are weak acids.
• We write the ionization of HF as:
HF  H+ + F–

15. Acid-Base Reactions
In an acid–base reaction, the acid donates a proton (H+) to the base.

16. Neutralization Reactions
Generally, when solutions of an acid and a base are combined, the products are a salt and water:
CH3COOH(aq) + NaOH(aq) CH3COONa(aq) + H2O(l)

17. Neutralization Reactions
When a strong acid reacts with a strong base, the net ionic equation is
HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)

18. Neutralization Reactions
When a strong acid reacts with a strong base, the net ionic equation is
HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
H+(aq) + Cl−(aq) + Na+(aq) + OH−(aq) 
Na+(aq) + Cl−(aq) + H2O(l)

19. Neutralization Reactions
When a strong acid reacts with a strong base, the net ionic equation is
HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
H+(aq) + Cl−(aq) + Na+(aq) + OH−(aq) 
Na+(aq) + Cl−(aq) + H2O(l)
H+(aq) + OH−(aq)  H2O(l)

20. The balanced molecular equation is:
The complete ionic equation is:
The net ionic equation is:

21. volume of solution in liters
Molarity
Two solutions can contain the same compounds but be quite different because the proportions of those compounds are different.
Molarity is one way to measure the concentration of a solution:
moles of solute
volume of solution in liters
Molarity (M) =

22. Mixing a Solution
To create a solution of a known molarity, one weighs out a known mass (and, therefore, number of moles) of the solute.
The solute is added to a volumetric flask, and solvent is added to the line on the neck of the flask.

26. Dilution One can also dilute a more concentrated solution by
Using a pipet to deliver a volume of the solution to a new volumetric flask, and
Adding solvent to the line on the neck of the new flask.

27. Dilution
The molarity of the new solution can be determined from the equation
Mc  Vc = Md  Vd
where Mc and Md are the molarity of the concentrated and dilute soln., respectively, and Vc and Vd are the volumes of the two solutions.

29. Using Molarities in Stoichiometric Calculations

30. Titration
Titration is an analytical technique in which one can calculate the concentration of a solute in a solution.

31. Titration

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