EDTA Titration and Water Hardness Calculation

EDTA Structure

EDTA (C₁₀H₁₆N₂O₈) is a hexadentate ligand that binds metal ions through four carboxyl (–COOH) groups and two amine (–NH₂) groups.

Titration Procedure (Water Hardness Test)

1. Take a 50 mL water sample.
2. Add buffer (pH 10) and Eriochrome Black T indicator (resulting in a wine-red color).
3. Titrate with EDTA until the color changes to sky blue (the end point).
4. Note the volume of EDTA used (V).

Reaction

M²⁺ + EDTA⁴⁻ → [M-EDTA]²⁻

Calculation Formula

Hardness (ppm) = (V × M × 1,000,000) / Vₛₐₘₗₔₗₑ

• M = EDTA molarity
• V = Volume of EDTA used (mL)
• Vₛₐₘₗₔₗₑ = Sample volume (mL)

Water Impurities and Boiler Problems

Hardness

The presence of calcium (Ca²⁺)

🔹 Isomerism (Class 11)

Definition:

Isomers are compounds having the same molecular formula but a different arrangement of atoms or different spatial arrangement, resulting in different properties.

1️⃣ Structural Isomerism

(Atoms have a different connection)

(A) Chain Isomerism

Definition:

Same molecular formula but a different carbon chain (straight or branched).

Example:

• C₄H₁₀
  • n-Butane → CH₃–CH₂–CH₂–CH₃
  • Isobutane → CH₃–CH(CH₃)–CH₃
• C₅H₁₂
  • Pentane
  • Isopentane
  • Neopentane

(B) Position Isomerism

Definition:

Same carbon chain and functional group, but the position of the functional group or multiple bond is different.

Example:

• C₃H₈O
  • 1-Propanol (–OH on C-1)
  • 2-Propanol (–OH on C-2)
• C₄H₈
  • 1-Butene
  • 2-Butene

(C) Functional

Determination of Water Hardness by EDTA Method

EDTA is the abbreviation for Ethylene Diamine Tetra Acetic acid.

Pure EDTA dissolves in water with great difficulty and in very small quantities. Conversely, its di-sodium salt dissolves quickly and completely. Hence, for common experimental purposes, the di-sodium derivative of EDTA is used.

EDTA is a hexadentate ligand. It binds metal ions present in water, such as $Ca^{+2}$ or $Mg^{+2}$, to form a highly stable chelate complex. These metal ions are bonded via oxygen or nitrogen atoms from the EDTA molecule. Therefore, this method is called complexometric titration.

Principle of the EDTA Method

The di-sodium salt of EDTA forms complexes with $Ca^{+2}$ and $Mg^{+2}$ as well as with many other metal... Continue reading "Determining Water Hardness: The EDTA Titration Method" »

1. Sources of Water

2. Impurities in Water

3. Hardness of Water

Definition

Hardness... Continue reading "Water Chemistry: Hardness, Alkalinity, and Treatment" »

Chemical Reactions

Types of Chemical Reactions

• Synthesis: A + B → AB
• Decomposition: AB → A + B
• Single Displacement: A + BC → AC + B
• Double Displacement: AB + CD → AD + CB
• Combustion: A + O₂ → H₂O + CO₂ (typically for hydrocarbons)
• Acid-Base: Acid + Base → Salt + Water
• Precipitation: Soluble Salt A + Soluble Salt B → Precipitate + Soluble Salt C

Stoichiometry and Mole Concepts

Key Stoichiometry Relationships

• Mass: 1 mole = Molar Mass (in grams)
• Volume: 1 mole = 22.4 L @ STP (Standard Temperature and Pressure)
• Particles: 1 mole = 6.022 × 10²³ particles (Avogadro's Number)
• Mole-Mole Conversions: Use coefficients from a balanced chemical equation.

Standard Temperature and Pressure (STP)

• Temperature: 0 °C (273.15 K)
• Pressure: 1 atm

Gas Laws

Answer Key for Solubility Equilibrium

1A, 2C, 3B, 4C, 5A, 6C, 7C, 8B, 9A, 10D, 11D, 12A, 13B, 14C, 15C, 16D, 17B

Detailed Solutions for Solubility Problems

Problem 1: Net Ionic Equation and Precipitation

1a. Net Ionic Equation:
Pb²⁺ + 2Cl^- → PbCl₂(s)

1b. Precipitation Calculation:
moles Pb²⁺ = (0.0150)(0.0500) = 0.00075
moles Cl^- = (0.0350)(0.0850) = 0.002975
total volume = 0.0500 L

[Pb²⁺] = 0.00075 / 0.0500 = 0.0150 M
[Cl^-] = 0.002975 / 0.0500 = 0.0595 M

Q = [Pb²⁺][Cl^-]² = (0.0150)(0.0595)²
Q = 5.3 × 10^-5
K_sp = 1.6 × 10^-5
Since Q > K_sp, a precipitate indeed forms.

Problem 2: Calculating Ksp for Silver Sulfate

2a. K_sp of Ag₂SO₄:
moles = mass / molar mass
moles = (7.2 × 10^-4) / 311.8 = 2.31 × 10^-6 mol

s = moles / volume
s = (2.31 × 10^-6) / 0.0500 = 4.62... Continue reading "Solubility Equilibrium and Ksp Practice Problems" »

Preparation of Naphthalene

Naphthalene is a fused-ring aromatic hydrocarbon with two benzene rings. It can be prepared via the following methods:

• From Coal Tar: Coal tar, a by-product of coal processing, is a major source of naphthalene. It is extracted and purified using distillation followed by crystallization.
• Synthesis from Benzene: Benzene undergoes a series of reactions to form naphthalene:
  • Alkylation: Benzene reacts with alkyl halides (like methyl chloride) to form methylbenzene (toluene).
  • Cyclization: Toluene undergoes further reaction with chlorine and heat to form naphthalene.

Preparation of Anthracene

Anthracene is a tricyclic aromatic hydrocarbon consisting of three fused benzene rings. It is mainly obtained from coal tar but can also... Continue reading "Synthesis and Sources of Aromatic Hydrocarbons" »

To convert from decimal inches. A fraction of an inch.
Multiplied by 128 to decimal and simplifying the result by 128.

Convert decimal to a fraction of an inch inch

Examples:
1) Convert 0.250 "a fraction of an inch
Applying the rule, we have: (0.250 "* 128) / 128 = 32/128 = ¼"
2) Convert 1.750 "a fraction of an inch
Applying the rule, we have: (1,750 '* 128) / 128 = 1 96/128 = 1 ¾ "
3) Convert 2.953 "a fraction of an inch
Applying the rule, we have: (2.953 "* 128) / 128 = 2 122/128 = 2 61/64"
4) Convert 12.812 "a fraction of an inch
Applying the rule, we have: (12.812 "* 128) / 128 = 12 104/128 = 12 13/16"


To convert from mm. A fraction of an inch. Should be carried mils.
(Divide by 25.4) and then multiplying by 128 and simplify

Anions: Definition and Characteristics

An anion is an ion (an atom or molecule) that possesses a negative electrical charge, meaning it has an excess of electrons. Anions are typically described with a negative oxidation state. They are broadly classified into two main types: monatomic and polyatomic.

Monatomic Anions

Monatomic anions are typically formed when nonmetals gain electrons to complete their valence shell.

Traditional Nomenclature (Monatomic)

These are named using the word ion followed by the name of the nonmetal, ending in the suffix -ide. (Note: Amide and Cyanide are often included here for simplicity, though technically polyatomic.)

• Cl^-: Chloride ion
• H^-: Hydride ion
• S^2-: Sulfide ion
• NH₂^-: Amide ion
• CN^-: Cyanide ion

Systematic Nomenclature