# Concentration and Dilutions - drbperiodcsem2

```Jackielyn Jabson
Friday, March 16, 2014
Solutions Unit
Dilution
Lesson Date: Friday, May 16, 2014
IN CLASS
PowerPoint on Dilution
Sheet Name: Concentration & Dilutions
Sheet Number: H3
HOMEWORK
↘ Complete “More Dilution Practice” on Concentration & Dilutions sheet (H3)
↘ Textbook questions on p. 405 #2 – 7 (Dilutions Review) and p. 411 #1-10 (more Concentration of
Solutions Review)
Answers to More Dilution Practice Questions:
Concentration and Dilutions
Lesson Summary:
What is Dilution?
Dilution is the process of reducing the concentration of a solution by adding more solvent. The number of
moles of solute remains the same because solute is neither being taken out or being added. More solvent
(water – a universal solvent) is only being added to the solution. The result of the dilution would be that there
is less solute (in moles) per volume of the solution.
More moles of solute
per volume
Less moles of solute
per volume
=
=
Concentrated solution
Diluted solution
How to Prepare a Dilution?
Dilutions involve transferring accurate volumes of a concentrated solution into another container. In order to
prepare dilutions, a volumetric pipette and volumetric flask are used because there is less surface area for air
due to their small diameter and thus will be more accurate; compared to a graduated cylinder which has a
larger diameter.
1
Jackielyn Jabson
Friday, March 16, 2014
Dilution Calculations:
During dilution, the amount of solute (in moles) does not change. The concentration changes because the
volume of the solution increases.
Remains constant (amount of solute)
Decreases
(because volume
increases)
=

The final concentration of the dilute solution can be determined by using a mathematical equation:
Dilution Equation
Concentrated Solution
Diluted Solution
C1V1 = C2V2
Initial
Concentration
NOTE:
Final
Initial
Concentration
Volume
Final
Volume
↘ Since moles remain constant, when you have two solutions, a concentrated solution and diluted
solution, the two equations above can be made equivalent to one another
↘ Concentration and volume have an inverse relationship (as one increases, the other decreases)
↘ Initial & Final Volumes and Concentrations MUST all have the same units
EXAMPLE
A stock solution of 1.00M of NaCl is available. How many millilitres are needed to make a 100.0mL of 0.750M?
Step 1: Determine the information given
Given
C1 = 1.00M
V1 =?
C2 = 0.750M
V2 = 100mL
Step 2: Write down the equation and plug in the information given
C1V1 = C2V2
1.00M x V1 = 0.750 x 100mL
Step 3: Rearrange equation to solve for the unknown (in this case the unknown is the initial volume)
=
0.750  100
1.00
Step 4: Solve equation
= 75
∴ 75mL are needed.
NOTE:
↘ The given volume was NOT needed to be converted from millilitres into litres because the mol/litre (M)
↘ BEWARE if the question asked for the answer to be litres, the 75mL would have to be converted to
litres (by dividing 75mL by 1000L)
2
Jackielyn Jabson
Friday, March 16, 2014
Resources on Dilution
Textbook Chapter: 8.7 Preparing Dilutions
p. 403 – p. 405
Further explanation regarding dilutions and more practice questions with answers provided:
http://dl.clackamas.edu/ch105-04/dilution.htm