Chemistry Practicals For HSC-Part 1 (XI -Science Group) - Experiment No.2 : Titration (KOH - H2SO4)

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TITRATION

By D. J. Sindh Govt. Science College
OBJECT:
(2) You are given decinormal (1/ 10 or 0.1 N) solution of KOH. Find out Normality and amount of given H₂SO₄ per 100 cm³ solution.

APPARATUS:

• Burette
• Pipette
• Conical Flask
• Burette Stand with clamp
• Dropper

THEORY:
ACID-BASE TITRATION:
Titration is a process in which the fixed volume of a solution taken by means of pipette into conical flask is compared with the volume of solution added from burette upto end point which is obtained by colour change. The purpose of titration is to determine the unknown strength of a solution.
Base is a substance which gives OH^- ion in aqueous solution. When an acid solution reacts completely with base solution or vice versa, a salt is formed.
Neutralization: In acid-base reaction H⁺ ion from an acid and OH^- ion from a base form H₂O, salt is also formed process is called neutralization. This is indicated by end point and is observe by suitable indicator those having different colors in different medium.
Strong acid and strong base ionize completely in aqueous solution while weak acid and weak base ionize only partially in aqueous solution, these form acidic and basic salts which hydrolyse to change the pH.

Na₂CO₃ + H₂O ⟶ NaOH + H₂CO₃

(Basic salt) + (water) (Strong base) (Weak acid)

where Basic (pH > 7)

EQUATIONS

2KOH + H₂SO₄ ⟶ K₂SO₄ + 2H₂O

IONIC EQUATION

2K⁺ + 20H^- + 2H⁺ + SO₄^2- ⟶ 2K⁺ + SO₄^2- + 2H₂0

PROCEDURE:
Strong Base Vs Stron Acid

1. Wash burette, pipette and conical flask with water.
2. Rinse burette with base (KOH) and pipette with acid (H₂SO₄).
3. Do not rinse the conical flask.
4. Fill the burette with base (KOH) upto Zero mark.
5. Pipette out 10 cm³ of acid (H₂SO₄) into the conical flask.
6. Add one or two drops of phenolphthalein as indicator.
7. Titrate the base in the burette with the acid in conical flask. The burette solution is added drop by drop into the conical flask.
8. Shake the flask after each addition, The end point is indicated by colour change from colourless to light pink.
9. Note the end point.
10. Wash the conical flask with water and repeats the same process for at least three times to obtain two similar readings.

OBSERVATION:
Volume Of NaOH = V₁ = ___ cm³

S.NO.	Initial reading	Final reading	Difference	Concordant reading
1.	cm3	cm3	cm3	___ cm3
2.	cm3	cm3	cm3
3.	cm3	cm3	cm3

• Solution in burette = KOH
• Solution in conical flask = H₂SO₄
• Indicator used = Phenophthalein
• Normality of standard solution Of KOH = N₁ = 0.1 N
• Volume of KOH solution = V₁ = _____ ml (Hint: Burette - concordant reading)
• Normality of H₂SO₄ solution = N₂ = ___ N
• Volume of standard solution Of H₂SO₄ = V₂ = 10 ml
• Amount of H₂SO₄ = _____ gms/cm³

CALCULATION:
Normality Of H₂SO₄

N_{1 (base)} x V_1(base) = N_{2 (acid)} x V_{2 (acid)}
OR

N₂ = (N₁ x V₁) / V₂ = ____ N

Equivalent mass Of H₂SO₄ = Molecular mass / Basicityty of H₂SO₄
Molecular mass of H₂SO₄ = 2(1) + 1(32) + 4(16) = 2 + 32 + 64 = 98 a.m.u
Equivalent mass Of H₂SO₄ = 98 / 2 = 49

Amount Of H₂SO₄ In gms / 100 cm³

RESULT:
Normality of given H₂SO₄ solution = ______ N
Amount of H₂SO₄ in the given solution = ____ gms / 100 cm³

OR

By Mubarka Naz
EXPERIMENT NO.2
OBJECT: You are provided N/18 (0.56 N) Solution of H₂SO₄. Determine the normality and amount of KOH in gms per 600 cm³.

APPARATUS:

• Burette
• Pipette
• Conical Flask
• Burette Stand
• Clamp with holder
• Dropper

THEORY:
When an acid reacts completely with an equivalent amount of a base neutralization takes place. Neutralization is the process in which H⁺ ion of an acid and OH^- ions of a base combine to form water. A salt is also formed during the neutralization.

Acid + Base ⟶ Water + Salt

EQUATION:

2KOH + H₂SO₄ ⟶ K₂SO₄ + 2H₂O

IONIC EQUATION:

2K⁺ + 20H^- + 2H⁺ + SO₄^2- ⟶ 2K⁺ + SO₄^2- + 2H₂0

PROCEDURE:
1) Wash the burette pipette and conical flask with water.
2) Rinse the burette with KOH solution and pipette with H₂SO₄ solution.
3) Fill the burette with KOH solution leaving no air bubble in the jet and clamp it vertically in to the burette stand.
4) Pipette out 10 cm³(ml) of H₂SO₄ solution in to the conical flask and add 1 - 2 drops of phenolphthalein indicator.
5) Start adding the solution of NaOH drop by drop from the burette into the conical flask, shake the flask after each addition.
6) Continue the addition of KOH solution till a permanent pinkish tinge appears with a single drop of KOH solution, record the reading of burette at this stage.
7) Wash the conical flask with water and repeat the process of titration till concordant reading is obtained.

OBSERVATIONS:
i) Solution in burette: KOH
ii) Solution in conical flask: H₂SO₄
iii) Normality of Acid: 0.56 N
iv) Normality of base: ? N
v) Indicator: Phenolphthalein
vi) Change of colour: colourless to pink

OBS Nos.	Initial Reading Of Burette (X cm3)	End Point Reading Of Burette (Y cm3)	Volume consume (Y - X cm3)
1.	0	8.0	8.0
2.	8.0	16.0	8.0
3.	16.0	24.0	8.0
4.

Concordant Reading = (8.0 + 8.0 + 8.0) / 3 = 8.0 cm³

CALCULATIONS:

RESULT:
Normality of the given KOH solution = ___ N or gram.equivalent/ltr/dm³.
Amount of KOH in the given solution = _____ gms / 600 cm³.