Transcript Chapter 16: Solutions

CHAPTER 16: SOLUTIONS
Properties, Concentrations, and Dilutions
REVIEW
Solute and Solvent
Solute is the substance being dissolved.
Solvent is the substance doing the dissolving.
Example: Salt and Water. We dissolve salt in water.
Therefore, the salt is the solute and the water is the solvent.
Why is water called the universal solvent?
PART 1: PROPERTIES OF
SOLUTIONS
Forming a Solution
• The composition (what they are made out of) of the solvent and solute
determine whether a substance will dissolve.
How FAST will the substance dissolve?
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•
•
•
This depends on three things:
1. Stirring: Increase of decrease rate?
2. Temperature: Increase or decrease rate?
3. Particle Size: The more surface area exposed, the faster it will dissolve.
PART 2: SOLUBILITY
What amount of a substance will dissolve?
Particles move from a solid into a solution. But how
much can be dissolved?
Solubility describes the amount of substance that can
be dissolved by a certain quantity of a solvent at a
certain temp and pressure until the solution becomes
saturated.
SOLUBILITY
Different Types of Solutions:
• Saturated Solution: The maximum amount of solute that can be dissolved
at a specific temp and pressure.
• Unsaturated Solution: A solution that contains less solute than required to
be a saturated solution and a certain temp and pressure.
• Supersaturated Solution: contains more solute than it can theoretically hold
at a given temperature.
• Miscible Solution: when two liquids will dissolve into one another. There is
no separation.
• Immiscible: liquids that are not soluble in each other. You can tell if it is
immiscible by observing layers.
SOLUBILITY
Miscible
Water and
Acetone
Immiscible
Oil and Water
SOLUTIONS
Supersaturated
Solution
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What do YOU think?
What type of solution is being utilized?
How are they making that solution?
FACTORS THAT AFFECT
SOLUBILITY
• 1. Temperature: Solubility of
MOST substances increases
as temperature increases.
• You can dissolve more
solute in the solvent as you
increase the temperature.
Think about how we made
our rock candy.
• EXCEPTION: Gas
solubility increases as
temperature
decreases.
FACTORS THAT AFFECT
SOLUBILITY
• 2. Pressure: Changes in pressure doesn’t affect the solubility of solids and
liquids, but it greatly influences the solubility of gases.
• As pressure increases, the solubility of gases also increases. Use Henry’s
Law for calculations.
• S = solubility
• P = pressure
• Directly Proportional
SOLUBILITY OF SOLUTIONS
How would I describe solubility in terms of UNITS?
Solubility is usually expressed in grams of solute per 100g of
solvent.
•
Example: 36g of sodium chloride in 100g of water at 25
degC.
•
Examples in terms of saturation: If 36g of NaCl is added to
100g water, it will dissolve completely, but if I added 1 more
gram of NaCl, only 0.2g of that will dissolve. Therefore,
36.2g of NaCl in 100g of water is a SATURATED solution.
•
How would I make it super saturated??
PART 3: CONCENTRATIONS
Concentration: a measure of the amount of solute that is dissolved in a given
quantity of solvent.
Dilute Solution: a weak concentration. Contains small amount of solute.
Concentrated Solution: strong concentration. Contains a large amount of
solute.
Concentrated
Dilute
CONCENTRATIONS
MOLARITY
Moles of solute dissolved in 1 Liter of solution.
LET’S MAKE A SOLUTION
Let’s determine the
molarity of a solution
that we make. Let’s
start with 10 grams
of sodium chloride
and add it to a 1-L
volumetric flask half
filled with distilled
water.
LETS MAKE A SOLUTION
Swirl the flask
carefully to dissolve
the solute.
LETS MAKE A SOLUTION
Fill the flask with
water exactly to the
1-L mark.
What is the
concentration of
the solution in
molarity?
Answer: 0.171M
LETS MAKE A SOLUTION
This will work with ANY volumetric flask. Big or small. We can
then calculate the molarity (concentration) of our solution.
• How do we convert mL to L?
WHAT IF YOU KNOW THE
MOLARITY?
Find the number of moles of solute in a solution…
• We can also convert moles to grams.
DILUTIONS
Diluting a solution reduces the number of moles per unit volume. The
number of moles of solute remains unchanged.
Dilution equation:
DILUTIONS
To prepare 100 ml of
MgSO4 from a stock
solution of 0.171M
NaCl, a student first
measures 10 mL of
the stock solution
with a 10-mL pipet.
DILUTIONS
She then transfers
the 10 mL to a
100-mL volumetric
flask.
DILUTIONS
Finally, she
carefully adds
water to the
mark to make
100 mL of
solution. What is
the final
concentration?
Use M1 x V1 = M2 x V2
Answer: 0.0171
TO MEASURE VOLUME
Some volume measuring
devices…
Buret
Graduated Cylinder
Volumetric Flask
Glass Pipets
DILUTION CALCULATION
PERCENT CONCENTRATIONS OF
SOLUTIONS
These are not as common as molarity, but are used sometimes .
Percent by volume:
Percent by mass:
PERCENT CONCENTRATION
CALCULATIONS
Percent by volume: (volume/volume)
PERCENT CONCENTRATION
CALCULATIONS
Percent by mass: (mass/mass)
• Suppose you want to make a 2000g solution that has
a 2.8% (m/m) concentration of glucose in water.
• How many grams of glucose should you use?
CLASS WORK
Page 499
# 42, 44, 46, 48, 49a, 51, 52, 53a,b, 54a, 55a