1. Dilution of Solutions

2. Dilution of Solutions add water concentrated dilute acid acid
MOLES ARE THE
SAME
Dilution is the process of decreasing the concentration of a solution by adding more solvent. This does not change the amount of solute, just its concentration.

3. Concentrated sulphuric acid has a concentration of 18 mol/L
Concentrated sulphuric acid has a concentration of 18 mol/L. What volume should be used to prepare 2.00 L of 1.00 mol/L sulphuric acid?
Step 1: Using what is given, calculate the number of moles of the dilute solution.
nD= cDVD
= (1.00 mol/L)(2.00L)
= 2.00 mol n c V

4. Step 2: Remember the number of moles are the same in both the concentrated and the diluted solution.
nD = nC = 2.00 mol

5. The volume of concentrated acid required is 0.11 L
Step 3: Use the number of moles from the dilute solution to calculate the volume of the concentrated acid required.
vC = =
=0.11L
The volume of concentrated acid required is 0.11 L nC cC
2.00 mol
18 mol/L

6. Step 4: Calculate how much water was needed to make this solution
Vwater= volume of solution – volume of acid
= 2.00 L – 0.11 L
= 1.89 L
To make this solution, add 0.11 L concentrated acid and 1.89 L of water.

7. Because the number of moles will not change, we can use the formula:
CiVi=CfVf
Ci =initial concentration of the solution
Vi= initial volume of the solution
Cf= final concentration of the solution
Vf= final volume of the solution

8. For a chemistry lab, you need a 2. 0L of 0. 10 M of H2SO4
For a chemistry lab, you need a 2.0L of 0.10 M of H2SO4. This acid is usually sold as 18 M. How much initial water did you have?
Ci =18M Vi= ? L Cf= 0.1M Vf= 2.0L
CiVi=CfVf
Vi=CfVf Ci
Vi=(0.10M)(2.0L) / 18M
= 0.01L

9. Herman has to dilute a 2.0mol/L copper (II) sulfate solution with a volume of 0.63L to make a 250mL solution. What is the final concentration?
Ci =2.0M Vi= 0.63 L Cf= ? M Vf= 250mL
CiVi=CfVf
Cf=CiVi Vf
Cf=(2.0M)(0.63L) / .25L
= 0.5M

10. Preparing Solutions
To prepare solutions, volumetric flasks (usually 1L) are used. There is a standard procedure for preparing these solutions.
Measure out mass of solute on a scale
Partially fill the volumetric flask with water
Use a funnel to transfer the mass over to the flask. Swirl it around to dissolve the solute
Continue to add water to the line (bottom of meniscus should be at the etched line)
Transfer solution to alternate bottle to store.