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?!?!?!
VS
Dilution
-which one has a higher molarity?
Amount of solute is constant
Amount of solvent increases
Amount solute in concentrated solution
EQUALSAmount solute in dilute
solution
Dilution = add water = less concentrated
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
300ml
2.5M 2.5M
?M
750ml
water
1M
So how much water did we have to add to delete the 2.5 M solution? 750
-300 _ 450ml
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
So what does 65 ml tell us?!V1 = 0.065 L = 65 mL
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)