Unit-1. Volumetric Analysis

🔹 Unit 1: Volumetric Analysis (8 Teaching Hours)

🧪 1. Introduction

a. Gravimetric Analysis

It is a quantitative analysis method where the amount of substance is determined by measuring mass.
Example: Determination of sulfate as BaSO₄.

b. Volumetric Analysis

It is a method of quantitative chemical analysis used to determine the concentration of a solute in a solution by measuring the volume of a standard solution required to react completely.
Example: Titration of HCl with NaOH.

⚖️ 2. Equivalent Weight

Definition: The equivalent weight of a substance is the amount that reacts with 1 mole of H⁺ ions or 1 mole of electrons in redox reactions.

a. Relationship between Equivalent Weight (E), Atomic Weight (A), and Valency (V):

$E = \frac{A}{V}$

📋 3. Equivalent Weight of Compounds

Compound Type	Formula
Acid	$\text{Eq. wt.} = \frac{\text{Molecular wt.}}{\text{Basicity}}$
Base	$\text{Eq. wt.} = \frac{\text{Molecular wt.}}{\text{Acidity}}$
Salt	Depends on ions replaced during reaction
Oxidizing Agent	$\text{Eq. wt.} = \frac{\text{Molecular wt.}}{\text{No. of electrons accepted}}$
Reducing Agent	$\text{Eq. wt.} = \frac{\text{Molecular wt.}}{\text{No. of electrons donated}}$

🧂 4. Concentration of Solutions

Unit	Description
% (w/v)	Grams of solute per 100 mL solution
g/L	Grams of solute per liter of solution
Molarity (M)	Moles of solute per liter of solution
Molality (m)	Moles of solute per kg of solvent
Normality (N)	Equivalents of solute per liter of solution
Formality (F)	Formula units per liter (used for ionic compounds)
ppm	Parts per million (mg/L)
ppb	Parts per billion (μg/L)

🧪 5. Primary and Secondary Standard Substances

Type	Description	Examples
Primary Standard	Pure, stable, non-hygroscopic, high molar mass, used to prepare standard solutions	K₂Cr₂O₇, Na₂CO₃, Oxalic acid
Secondary Standard	Solutions standardized against primary standards	KMnO₄, HCl, NaOH

⚖️ 6. Law of Equivalence

Statement: In a chemical reaction, equivalents of one substance = equivalents of another.
Normality Equation:

$N_1V_1 = N_2V_2$

Where:
$N_1$ = normality of acid, $V_1$ = volume of acid
$N_2$ = normality of base, $V_2$ = volume of base

🧪 7. Titration

a. Definition

Titration is a method to determine the unknown concentration of a solution using a solution of known concentration.

b. Types of Titration

Type	Description
Acid-Base Titration	Involves neutralization reaction between acid and base
Redox Titration	Involves electron transfer reaction between oxidizing and reducing agents

c. Indicators Used

Titration Type	Indicator
Strong acid + strong base	Phenolphthalein or Methyl orange
Weak acid + strong base	Phenolphthalein
Redox titration	Self-indicator (KMnO₄) or external (starch for I₂)

🧮 8. Related Numerical Problems

Example 1:

Calculate the normality of a solution prepared by dissolving 4.9 g of H₂SO₄ in 500 mL of solution.
Molecular wt of H₂SO₄ = 98, Basicity = 2

$\text{Eq. wt.} = \frac{98}{2} = 49 \\ \text{Normality (N)} = \frac{\text{mass in g} \times 1000}{\text{Eq. wt.} \times \text{volume in mL}} = \frac{4.9 \times 1000}{49 \times 500} = 0.2 N$

Example 2:

25 mL of 0.1 N HCl is completely neutralized by NaOH. Calculate the volume of 0.05 N NaOH used.

$N_1V_1 = N_2V_2 \\ 0.1 \times 25 = 0.05 \times V_2 \Rightarrow V_2 = \frac{2.5}{0.05} = 50\ \text{mL}$

📷 Suggested Diagrams (Insert manually)

Volumetric apparatus (Burette, Pipette, Conical Flask)
Acid-base titration setup
Titration curve for strong acid–strong base
Color change of indicators