Lecture 4: Aqueous solution chemistry
Lecture 4 Topics
Brown, chapter 4
1. Solutes & solvents
4.1
• Electrolytes & non-electrolytes
• Dissociation
2. Solution concentration & stoichiometry
• Molarity & interconversion
• Dilution
4.5 – 4.6
Types of aqueous chemial reactions
3. Precipitation reactions
• Complete ionic equations
4. Neutralization reactions
• Acids & bases
• Neutralization reactions
• Non-hydroxide bases produce gases
• Titration
4.2
4.3
4.6
• Summary of complete ionic equations
5. Reduction & oxidation reactions
• Oxidation numbers
• Oxidation of metals by acids & salts
• Activity series
4.4
Aqueous Solution Chemistry
Electrolytes are conductive solutions
Solutes are present in lesser amounts.
Solvents are present in greater amounts.
Electrolytes dissociate, or come apart.
Solutes & solvents
What’s the difference between a solvent & a solute?
Solvent: The chemical found in larger amounts; it’s the bulk of a solution (often H2O).
Solute: The chemical found in smaller amounts; what’s dissolved in the solvent.
Inorganic chemistry involves several classes of solutes:
• Electrolytes compounds that dissociate in water; come apart into ions or elements
• Electrolytes conduct electricity; pure water does not!
•Strong - salts & strong acids (NaCl, KBr, CaCl2, HCl, HBr)
•Weak - weak acids like acetic acid (HC2H3O2)
•Non-electrolytes
molecular compounds that do not come apart in water (sugar)
• Non-electrolytes merely become diluted in water.
p.120-2
Dissociation? What & Why
How & why do salts dissociate in water?
It all starts with water!
Water is a dipolar
molecule; it has
partial +/- charges
on H/O ends.
H
K+
Cl-
Cations associate
with H2O’s - end.
Anions with its + end.
salts dissociate
compounds dissolve
This process is known
as ‘solvation’.
Ions ‘prefer’ to assoc.
with water because
it is by far the most
abundant molecule
in the solution.
Its numbers overcome
its weak charge.
p.120-2
Dissociation: compounds ionize
When ionic compounds dissociate, they produce ions according to
ratios (stoichiometry) present in the ionic compound’s formula.
1 Mg+2
MgCl2
3 ions for every one molecule
2 Cl-1
1 K+1
3 ions for every one molecule
KCl
1 Cl-1
2 K+1
K2(SO4)
3 ions for every one molecule
1 (SO4)-2
p.122-4