Concentration of Solutions

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TOPIC: Concentration and Dilution
Do Now:
Parts of a Solution
• Solute = dissolved substance
• Solvent = dispersing medium
We can determine how much solute and solvent
make up a solution = CONCENTRATION
Concentration = A measurement that
describes how much solute is in a given
amount of solvent or solution.
Many, many different units to express concentration.
• Molarity
• PPM (parts per million)
• % by mass
• % by volume
Molarity (M)
Molarity (M) = moles of solute
liters of solution
CAN USE THIS TO
HELP CALCULATE
moles
M
liters
So why do aqueous
solutions need .1M or 3M
in front?!?!?!
Dilution
-which one has a higher molarity?
Dilution = add water = less
concentrated
Amount solute in
concentrated solution
EQUALS
Amount solute in dilute
solution
Amount of solute is
constant
Amount of solvent
increases
MolarityC x VolumeC = MolarityD x VolumeD
MC x VC = MD x VD
(C = concentrated
D = dilute)
300ml of 2.5M NaOH is diluted to 750ml.
Find the molarity of the diluted solution
MC x VC = MD x VD
300ml x 2.5M = 750ml x MD
So how much water did
we have to add to delete
the 2.5 M solution?
2.5M
300ml
water
750
-300 _
450ml
?M
1M
2.5M
750ml
Example: We are doing a lab and the procedure
calls for 300ml 1.2 M NaOH. However, all we
have is a bottle of 5.5M NaOH.
We have to dilute it!!!!
The Equation: MC x VC = MD x VD
5.5 M x VC = 1.2 M x 300ml
V1 = (1.2 M x 300 ml)
5.5 M
V1 = 0.065 L = 65 mL
So what does 65 ml tell us?!
To prepare the 1.2 M NaOH solution, you
pour 65 mL of 5.5 M NaOH into your
container and add water to get 300 mL final
volume (300-65 = 235 ml water added)
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