8. The Hydronium Ion
a) Acids release a proton (H+) when mixed with water!
HCl(g) H+(aq) + Cl-(aq)
b) What Happens to a Proton in Water?
i) H+ is very positive and is therefore strongly attracted to anything negative.
ii) H2O molecule has a negative part
1. Acid and Base Titration Calculations
a) Strong Acid and Strong Base
i) Example: We have 150 mL of NaOH at an unknown concentration. 75 mL
of 0.300 M HCl must be added to reach the equivalence point. What is
HCl + NaOH H2O + NaCl
Moles HCl = M x
prevents a significant change in pH when acid or base is added
0.1 mol HCl added to water
pH changes 6 units! (7 to 1)
0.1 mol HCl added to water
containing buffer system
pH changes only 0.08 units!
b) Acidic Bu
6. Electrochemical Cell - Quantitative
Voltage along the wire in an electrochemical cell depends on the half reactions.
a) Cell Potential
i) cell potential (E cell) is the maximum voltage of an electrochemical cell
ii) standard cell potential (Ecell) is t
5. Electrochemical Cell Applications
a) Factors Affecting Electrochemical Cells
a change means not 1 M (so the is removed from the E cell)
apply Le Chateliers principle:
eg/ Ag+ + e-
E cell = +0.80 V if [Ag+] = 1 M
a + E cell mea
Electrochemical cell spontaneous redox reaction produces electricity
Electrolysis add electricity to non-spontaneous reactions to make them go!
a) Electrolysis of Water
Water will NOT spontaneously reduce to H2:
2H2O + 2e- H2 + 2OH-
9. Oxidation vs. Reduction
a) Two Reactions in One!
i) Al (s) + Fe2O3 (s) Fe (l) + Al2O3 (s)
ii) There are two half reactions occurring!
Al (s) Al+3
(Al (s) loses 3 electrons)
Fe+3 Fe (l)
(Fe+3 gains 3 electrons)
iii) We must balance the half reactions
11. pH and pOH Calculations with Weak Acids and Bases
a) Weak Acids
i) Example: What is the pH of 0.400 M H2S?
Not 100% dissociated so [H2S] [H3O+]; so cant just pH = -log[0.400]
The weak acid will form an equilibrium:
H2S + H2O (l)
Salts dissociate 100% in water
The ions from the salt will either:
Be Spectator Ions
a) What is Hydrolysis?
i) Reaction between an ion from the salt with water.
ii) The ion will react with water to form a basic solution if
12. Electrochemical Cell Qualitative
Electrons are exchanged between two connected half-reactions.
Movement of electrons is electricity.
How can we harness the electricity from the following redox reaction?
13. Redox Titrations
Find an unknown concentration by slowly adding a known concentration until the
a) Find Concentration of a Reducing Agent
i) Procedure: 1. Titrate the reducing agent with KMnO4 (powerful oxidizing agent)
2. The reduc
10. Balancing Redox Reactions Using Oxidation
a) What are Oxidation Numbers?
Sample: K2Cr2O7 K is +1 Cr is +6
O is -2
They are not actual charges!
They are a bookkeeping system used to keep track of an atoms electrons!
i) Rules for Assigning Oxi
2. Acid/Base Titration The Basics
a) The Technique
i) The Purpose to find out concentration of an unknown acid or base.
ii) Titration means to slowly and accurately add known [acid] to an unknown
[base] (or vice versa) using a buret, until base is exactly