Chemistry Practicals For HSC-Part 1 (XI -Science Group) - Experiment No.1 : Titration (NaOH - HCl)

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TITRATION

By D. J. Sindh Govt. Science College
OBJECT:
(1) You are given 0.2 N solution of HCl. Find out Normality and amount of given NaOH per 1200 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

NaOH + HCl ⟶ NaCl + H₂O

IONIC EQUATION

Na⁺ + OH^- + H⁺ + Cl^- ⟶ Na⁺ + Cl^- + H₂O

PROCEDURE:
Strong Base Vs Stron Acid

1. Wash burette, pipette and conical flask with water.
2. Rinse burette with base (NaOH) and pipette with acid (HCl).
3. Do not rinse the conical flask.
4. Fill the burette with base (NaOH) upto Zero mark.
5. Pipette out 10 cm³ of acid (HCl) 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 = NaOH
• Solution in conical flask = HCl
• Indicator used = Phenophthalein
• Normality of standard solution Of NaOH = N₁ = ____ N
• Volume of NaOH solution = V₁ = _____ ml (Hint: Burette - concordant reading)
• Normality of HCl solution = N₂ = 0.2N
• Volume of standard solution Of HCl= V₂ = 10 ml
• Amount of NaOH = _____ gms/cm³

CALCULATION:
Normality Of NaOH

N₁ x V₁ = N₂ x V₂
OR

N₁ = (N₂ x V₂) / V₁ = ____ N

Equivalent mass Of NaOH = Molecular mass / Acidity of NaOH
Equivalent mass Of NaOH = 40 / 1 = 40

Amount Of NaOH In gms / 1200 cm³

RESULT:
Normality of given NaOH solution = ______ N
Amount of NaOH in the given solution = ____ gms / 1200 cm³

OR

By Mubarka Naz
EXPERIMENT NO.1
OBJECT: Given 0.1 N Solution of NaOH. Determine the normality and amount of HCl in gms per 800 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:

HCl + NaOH ⟶ H₂O + NaCl

IONIC EQUATION:

H⁺ + OH^- + Na⁺ + OH^- ⟶ H₂O + Na⁺ + Cl^-

PROCEDURE:
1) Wash the burette pipette and conical flask with water.
2) Rinse the burette with NaOH solution and pipette with HCl solution.
3) Fill the burette with NaOH solution leaving no air bubble in the jet and clamp it vertically in to the burette stand.
4) Pipette out 10 cm³(ml) of HCl 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 NaOH solution till a permanent pinkish tinge appears with a single drop of NaOH 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: NaOH
ii) Solution in conical flask: HCl
iii) Normality of Acid: ?
iv) Normality of base: 0.1 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	6.1	6.1
2.	6.1	12.2	6.1
3.	12.2	18.2	6.0
4.	18.2	24.3	6.1

Concordant Reading = (6.1 + 6.1 + 6.0 + 6.1) / 4 = 6.075 cm³

CALCULATIONS:

RESULT:
Normality of the given HCl solution = ___ N or gram.equivalent/Itr/dm³.
Amount of HCl in the given solution = _____ gms / 800 cm³.