7.3 COCENTRATION OF ACID AND ALKALI SLISS 2012

1. NURUL ASHIKIN BT ABD RAHMAN : UPSI

3. At the end of this lesson, students should be able to:
a)State the meaning of concentration and
b) State the meaning of molarity correctly.
c) State the relationship between the number
of moles with molarity and volume of a
solution.

4. Solvent...? Solute...?
Solution...?
Solution = Solvent + Solute

5. • The quantity of solute in a given volume of
solution. Which is usually a dm3.
3 mass of solute ( g )
Concentration ( g dm )
volume of solution (dm3 )
• Unit: g dm-3
• 1 dm3 = 1L= 1000 cm3 = 1000 mL

6. • The number of moles of solute that are present in
1 dm3 of solution.
3 number of moles of solute (mol )
Molarity (mol dm )
volume of solution (dm3 )
• Unit : mol dm-3

7. Molar mass
Molarity Concentration
(mol dm-3) (g dm-3)
Molar mass

8. Number of moles of solute,
n molarity ( M ) volume of solution (V )

9. EXAMPLE 1
Calculate:
a) The concentration of solutionin g dm-3 when
6.00 g of copper (II) sulphate is dissolved in
water to form 500 cm3 solution.
b) The molarity of solution when 0.8 mol of sodium
hydroxide is dissolvedin distilled water to form
250 cm3 of solution.

10. SOLUTION 1
a) Mass of copper (II) sulphate = 6.00 g
volume of solution = 500 cm3 = 0.5 dm3
Concentration = 6.00 g/0.5 dm3
= 12 g dm-3
b) Number of moles of NaOH = 0.8 mol
volume solution = 250 cm3 = 0.25 dm3
molarity of NaOH = 0.8 mol/ 0.25 dm3
= 3.2 mol dm-3

11. EXAMPLE 2
Calculate:
What is the mass of potassium hydroxide
required to dissolve in water to prepare a
200 cm3 solution that contains 30 g dm-3?
Answer: 6 g

12. EXAMPLE 3
Calculate:
0.2 mole of sodium carbonate is dissolved
in water to produced a solution with
concentration of 0.5 mol dm-3. What is the
volume of sodium carbonate solution?
Answer: 400 cm3

13. EXAMPLE 4
Calculate:
A copper (II) sulphate solution has a
concentration of 40.0 g dm-3. What is the
molarity of this solution in mole dm-3?
[relative atomic mass: O,16; S,32; Cu,64]
Answer: 0.25 mol dm-3 of CuSO4

14. EXAMPLE 5
Calculate:
The concentration of dilute hydrochloric acid in a
reagent bottle is 2.0 mol dm-3
a) What is the concentration of this solution in g
dm-3?
b) Find the mass of hydrogen chloride in 250 cm3
of the hydrochloric acid?
[relative atomic mass: H,1;Cl,35.5]

15. EXAMPLE 6
Calculate the number of moles of sodium
hydroxide in 25.0 cm3 of 1.5 mol dm-3
aqueous sodium hydroxide.
answer: 0.0375 mol

16. EXAMPLE 7
A 0.5 mol dm-3 potassium hydroxide solution
contains 7.0 g potassium hydroxide. Calculate the
volume of this solution.
[relative atomic mass: H,1; O,16; K,39]
answer: 0.25 dm3 / 250cm3

17. At the end of this lesson, students should be able to:
a)Describe methods for preparing standard
solutions.
b)Describe the preparation of a solution with a
specified concentration using dilution
method.
c) Relate pH value with molarity of acid and
alkali.
d)Solve numerical problems involving molarity
of acids and alkalis.

18. A standard solution is a solution where its
concentration is accurately known.
Prepare 100 cm3 of sodium hydroxide
solution with a concentration of 0.5 mol dm-3
1. Molecular mass? [Na,23;O,16;H,1]
2. Mass of NaOH?
3. Prepare solution.

19. Prepare 100 cm3 of sodium hydroxide solution with a
concentration of 0.5 mol dm-3
Solution:
Volume (V) = 100cm3 =0.1 dm3
Molarity (M) = 0.5 mol dm-3
Mass =?
Molar mass NaOH:
= 23+16+1 = 40 g mol-
Mole = mass/Molar mass

20. Mole (n) = Molarity (M) X Volume (V)
n = 0.5 mol dm-3 X 0.1 dm3
n = 0.05 mol
n = mass/molar mass
mass = n x molar mass
mass = 0.05 mol x 40 g mol-
mass = 2.0 g

21. 2.0 g of NaOH is weighed NaOH poured into a beaker
Containing distilled water

24. process of diluting a concentrated solution by
Dilution
adding water to get a more dilute solution.
M1 V1 = M2V2
M1: molarity of the solution before water is added
V1 : Volume of the solution before water is added
M2: molarity of the solution after water is added
V2 : Volume of the solution after water is added

25. Example :
90 cm3 of distilled water is added to 10 cm3 of a 1.0
mol dm-3 solution of HCl. Determine the molarity of
the diluted solution
0.1 mol dm-3

26. Prepare 500 cm3 of a 0.5 mol dm-3 of
Hydrochloric acid solution from 2.5 mol dm-3 of
HCl solution.
1. Calculate the volume of solution before
dilution? (V1)
2. The solution before dilution poured into
500 ml volumetric flask.
3. Water is added until reached graduation
mark.
4. Close with stopper, then shake it.

27. The higher the The higher the
molarity of acid, molarity of an
alkali, the higher
the lower the pH
the pH value.
value.

28. Example :
500cm3 of a solution that contains 2.0 mol sodium
hydroxide is added to 1500cm3 of a solution that contains
4.0 mol sodium hydroxide. Calculate the molarity of the
sodium hydroxide solution produced.

29. The End...