Download Solubility

Solubility
and pH
Solution = Solute + Solvent
Solvation
• Process of surrounding solute
particles with solvent particles to
form a solution
Video
Like Dissolves Like
• Polar substances dissolve polar
substances
• Nonpolar substances dissolve
nonpolar substances
EX: Demo
Styrofoam (nonpolar) + water (polar) = insoluble
Styrofoam (nonpolar) + acetone (nonpolar) = soluble
Factors Affecting the
Rate of Solvation
• To increase solvation of a solid
 Heat it (↑ temp.)
 Stir it (agitate the mixture)
 Crush it (↑ surface area)
• To increase solvation of a gas
 Cool it
 Increase pressure
Temperature and Pressure Change:
Solid vs. Gas
Pressure Change: Solid vs. Gas
Summary
Solids dissolve Gases dissolve the
best when
best when
Heated
Solution is cold
Stirred
Pressure is high
Crushed
Solubility
• Maximum amount of solute that
will dissolve in a given amount of
solvent at a specific temperature
and pressure
Types of Solutions
• Unsaturated – a
solution that can
dissolve more solute
• Saturated – a solution
that contains the
maximum amount of
solute that can
dissolve
• Supersaturated – a
solution that cannot
dissolve more solute
Practice
1. 80g of NaNO3 in
100g of H20 at
10⁰C
UnSaturated
2. 60g of KCl in 100g
H20 at 70 ⁰ C
Supersaturated
3. 150g of Kl in 100g
H2O at 25 ⁰ C
Saturated
Dissociation of Water
• Water splits into H+ & OH• H+ = hydrogen ion
• OH- = hydroxide ion
pH is a measure of how
much H+ is present
• 0 - 14
• 7 = neutral
• Negative
log scale
Dissociation of Water
Acids
• Acids are compounds that add
H+ ions to water when in a
solution – below pH of 7
Bases
• Bases are compounds that add
OH- ions to water when in a
solution – above pH of 7
pH Scale – Measure
of Acids and Bases
• When the pH changes from the pH of 7 in
the mouth to a pH of 2 in the stomach, how
many more times acidic is that ?
• 100,000 (power of ten)
Neutralization
• When acids and bases are mixed
they neutralize (cancel) each
other
Acid Rain
What are buffers?
*Buffers are substances that
maintain a particular pH so
that a reaction may occur
and at an appropriate rate .
*Chemical reactions in living organisms are very
sensitive to pH.
Buffer Example
Ex.:As the chyme moves from
the stomach into the small
intestine sodium bicarb buffers
the pH back up to 6.8 – a quick
change of almost a magnitude
of 100,000 decrease in acidity