1. Chapter 4 reaction in aqueous solution
4.5 Concentration of solutions
dilution of solutions
Dr.Laila Al-Harbi

2. 4.5 Concentration of solutions
The concentration of a solution is the amount of solute present in a given amount of solvent , it can be expressed in terms of its molarity (molar concentration)
Have mol and vol  molarity
Have molarity and vol  mol of solute
Have molarity and mol of solute  volume
AND: mol of solute  grams of solute
moles of solute
volume of solution in liters
Molarity (M) =
تذكري ان المولارية هي عباره عن عدد المولات على الحجم باللتر بعض الطالبات يعوضوا بالجرامات و ينسوا تحويلها الى مولات
Dr.Laila Al-Harbi

3. Questions in Molarity Given: n & V ↓ M Given: n & M ↓ V Given: V & M ↓

4. Dr.Laila Al-Harbi

5. Concentration of Solutions
What is the molar concentration of mol glucose C6H 12O6
in 500 ml solution
C6H 12O6 = mol C6H 12O6x 1000 mL soln
500 mL L soln
= 1.46 M C6H 12O6
Dr.Laila Al-Harbi

6. Dr.Laila Al-Harbi

7. 3.81g
Dr.Laila Al-Harbi

8. M= 0.452 M Practice exercise 4.6 Practice exercise 4.7
What is the molarity of an 85 ml ethanol C2H5OH solution containing 1.77g of ethanol?
Molar mass C2H5OH
= g
n = 1.77g/ = mol
M=n/v= mol/ 85 ml
M= M
What is the volume (in ml) of 0.315M NaOH solution contains 6.22g of NaOH?
Molar mass NaOH= 40g
n = 6.22g /40g= mol
v=n/M= mol / 0.315M
v= 0.494ι = 494 ml
Practice exercise 4.6
Practice exercise 4.7
Dr.Laila Al-Harbi

9. Dilution is the procedure for preparing a less concentrated solution from a more concentrated solution.
Calculation based on that the number of moles of solute is constant we add only solvent
Dilution
Add Solvent
Moles of solute
before dilution (i)
after dilution (f) =
MiVi
MfVf =
Dr.Laila Al-Harbi

10. Practice
How many mL of 5.0 M K2Cr2O7 solution must be diluted to prepare 250 mL of 0.10 M solution?
If 10.0 mL of a 10.0 M stock solution of NaOH is diluted to 250 mL, what is the concentration of the resulting solution?
Mi = 5.0M
Vf = 250 mL
Vi = ?
Mf = 0.10M Mi =
MfVf/Vi
Vi = 250 ml ×0.1M/5ml = 5 ml
Mf= ?
Vi= 10.0 mL
Mi = 10.0M
Vf = 250 mL Mi =
MfVf/Vi
Mi = 10ml ×10M/250ml = 0.4 ml
Dr.Laila Al-Harbi

11. How would you prepare 60.0 mL of 0.200 M
HNO3 from a stock solution of 4.00 M HNO3?
MiVi = MfVf
Mi = 4.00
Mf = 0.200
Vf = 60 ml
Vi = ? ml
Vi =
MfVf Mi =
0.200 x 60
4.00
= 3 mL
Dr.Laila Al-Harbi

12. Dr.Laila Al-Harbi

13. MiVi = MfVf Mi = 5.07 Mf = 0.866 Vf = 200 ml Vi = ? ml Vi = MfVf Mi =
Practice exercise 4.9
How would you prepare 200 mL of M NaOH from a stock solution of 5.07 M NaOH?
MiVi = MfVf
Mi = 5.07
Mf = 0.866
Vf = 200 ml
Vi = ? ml
Vi =
MfVf Mi =
0.866 x 200
5.07
= 34.2 mL
Dr.Laila Al-Harbi

14.  moles for the first Ca(NO3)2 solution (n1) = M1  V1
Problem 4.74 (page 163)
M1 = M V1 = 46.2 mL = 46.2  10-3 L
 moles for the first Ca(NO3)2 solution (n1) = M1  V1
= M  46.2  10-3 L = mol
M2 = M V2 = 80.5 mL = 80.5  10-3 L
 moles for the second Ca(NO3)2 solution (n2) = M2  V2
= M  80.5  10-3 L = mol
Total moles of Ca(NO3)2 in the final solution = n1 + n2
= = mol
Total volume of the final solution = V1 + V2
= (46.2  10-3 L) + (80.5  10-3 L) =  10-3 L
The concentration of the final solution Mf = n/V
= mol /  = 1.09 M
Calculation based on that we have two solutions with different number of moles mixed together , then we will calculate the molarity of the new solution
Dr.Laila Al-Harbi

15. volume of solution in liters
moles of solute
volume of solution in liters
Molarity (M) =
Molarity (M)
moles of solute = mass / molar mass
volume of solution in liters
Dr.Laila Al-Harbi