1. Solution Conductivity

2. Guiding Questions What is meant by dissociation?
What is the molecular arrangement of water molecules?

3. A. Definitions Solution - homogeneous mixture
Solute - substance being dissolved
Solvent - present in greater amount

4. Arrhenius’s Theory of Electrolytic Dissociation
Why do some solutions conduct electricity?
An early hypothesis was that electricity produced ions in solution, and those ions allowed the electricity to flow.
Arrhenius’s theory:
Certain substances dissociate into cations and anions when dissolved in water.
The ions already present in solution allow electricity to flow.

5. Dissociation

6. Nonpolar vs. Polar
When nonpolar substances dissolve in one another, they simply mix.
When polar substances dissolve, electrical reactions pull apart the molecules.

7. IONIC COMPOUNDS Compounds in Aqueous Solution
Many reactions involve ionic compounds, especially reactions in water — aqueous solutions.
K+(aq) + MnO4-(aq)
KMnO4 in water
To play the movies and simulations included, view the presentation in Slide Show Mode.

8. ELECTROLYTES
Are substances that form positive(+) and negative (-) ions in water
Conduct an electric current

9. Types of Electrolytes A strong electrolyte dissociates completely.
A strong electrolyte is present in solution almost exclusively as ions.
Strong electrolyte solutions are good conductors.
A weak electrolyte dissociates partially.
Weak electrolyte solutions are poor conductors.
Different weak electrolytes dissociate to different extents.
A nonelectrolyte does not dissociate.
A nonelectrolyte is present in solution almost exclusively as molecules.
Nonelectrolyte solutions do not conduct electricity.

10. Electrolytic Properties of Aqueous Solutions
Electrolytes dissociate to produce ions.
The more the electrolyte dissociates, the more ions it produces.

11. Is it a strong electrolyte, a weak electrolyte, or a nonelectrolyte?
Strong electrolytes include:
Strong acids (HCl, HBr, HI, HNO3, H2SO4, HClO4)
Strong bases (IA and IIA hydroxides)
Most water-soluble ionic compounds
Weak electrolytes include:
Weak acids and weak bases
A few ionic compounds
Nonelectrolytes include:
Most molecular compounds
Most organic compounds (most of them are molecular)
How do we tell whether an acid (or base) is weak?

12. B. Solvation Non- Electrolyte Weak Electrolyte Strong Electrolyte+
sugar - +
acetic acid - +
salt
Non-
Electrolyte
Weak
Electrolyte
Strong
Electrolyte
solute exists as
molecules only
solute exists as
ions and
molecules
solute exists as
ions only
DISSOCIATION
IONIZATION
View animation online.

13. Electrolytes in the Body
Make your own
50-70 g sugar
One liter of warm water
Pinch of salt
200ml of sugar free fruit squash
Mix, cool and drink
Carry messages to and from the brain as electrical signals
Maintain cellular function with the correct concentrations electrolytes