Notes, summaries, assignments, exams, and problems for Chemistry

Chemical Reactions and Equations

1. Chemical Reaction Definition

The process in which a substance undergoes change to produce new substances with new properties is known as chemical reaction, e.g., magnesium carbonate when heated produces magnesium oxide and carbon dioxide (i.e., new substances with new properties).

A chemical change is generally accompanied by a change of state, change of colour, evolution of a gas, or change of temperature, etc.

2. Chemical Equation Definition

The qualitative representation of a chemical reaction in a shorthand or concise form, in terms of symbols and formulae, is called a chemical equation.

3. Skeletal Chemical Equation

A chemical equation written in the form of symbols and formulae is called a skeletal chemical

Chemical Bonding Fundamentals

Definition and Purpose

Definition: Attractive forces holding atoms together in compounds.

Purpose: Atoms bond to achieve stability, often attaining a noble gas electron configuration.

Lewis Structures and the Octet Rule

Lewis Symbols

Dots represent valence electrons around elemental symbols.

The Octet Rule

Atoms tend to have eight electrons in their valence shell.

Limitations of the Octet Rule

It doesn't apply to all elements; some have incomplete or expanded octets.

Types of Chemical Bonds

• Ionic Bond: Electron transfer between atoms, forming charged ions.
• Covalent Bond: Sharing of electron pairs between atoms.
• Coordinate (Dative) Bond: Both shared electrons come from the same atom.

Bond Parameters

• Bond Length: Distance between

Structure of the Atom

Protons, Electrons, and Neutrons

Protons: Equal to the atomic number

Electrons: Equal to the atomic number

Neutrons: Equal to the atomic mass minus the atomic number

Bohr-Rutherford Diagram

Electron shells: 2, 8, 8, 18, 18, 32

Counting Atoms

Example 1: Na₂CO₃

• Sodium (Na): 2
• Carbon (C): 1
• Oxygen (O): 3

Example 2: 4Al₂(CO₃)₃

• Aluminum (Al): 4 x 2 = 8
• Carbon (C): 3 x 4 = 12
• Oxygen (O): 9 x 4 = 36
• Total: 56

Ions and Ionic Compounds

Ions are atoms that have either lost or gained electrons. While atoms are neutral, ions are charged particles.

Ionic Compounds are a combination of a cation (positive ion) and an anion (negative ion), typically formed between a metal and a nonmetal.

Example: Calcium Chloride (CaCl₂)

Calcium (Ca⁺²) has a charge of +2,... Continue reading "Structure of the Atom, Chemical Reactions, and Acids and Bases" »

What is a Dosage Form?

A dosage form may be defined as a blend of drugs and additives, produced in a definite physical form, size, and shape suitable for administration by a particular route.

Key Properties of Dosage Forms

• Economical
• Provides protection to the drug substance.
• Provides a better therapeutic effect.
• Easy to identify.
• Conceals bitter taste or odor.
• Easy to use and handle.
• Easy to store.
• Stable during use.

Importance and Need for Dosage Forms

The need for dosage forms, or their importance, is outlined below:

1. To protect the drug substance from oxidation, reduction, and hydrolysis (e.g., coated tablets, sealed ampules).
2. To provide a safe and convenient delivery of accurate dosage.
3. To mask the bitter, salty, or obnoxious taste or odor of a drug substance

Acid Value Determination in Oils: Principle and Procedure

Here's an explanation of the principle and procedure involved in determining the acid value of an oil sample:

Principle

The acid value of an oil sample is a measure of the amount of free fatty acids present in the oil. The principle of the acid value determination is based on the reaction between the free fatty acids in the oil and a strong base, such as potassium hydroxide (KOH). The reaction is as follows:

RCOOH (Free Fatty Acid) + KOH → RCOOK (Potassium Salt) + H₂O

Procedure

Here's the step-by-step procedure for determining the acid value of an oil sample:

1. Apparatus

• 250 mL Erlenmeyer flask
• Burette
• Pipette
• Volumetric flask
• Phenolphthalein indicator

2. Reagents

• Potassium hydroxide (KOH) solution

Alcohols, Thiols, Ethers, Aldehydes, and Ketones

1. Identifying Functional Groups

• Alcohol: -OH group attached to a carbon atom.
• Phenol: -OH group attached directly to a benzene ring.
• Thiol: -SH group (sulfhydryl group).
• Ether: C-O-C linkage (oxygen atom bonded to two carbon groups).
• Aldehyde: -CHO group (carbonyl group at the end of a chain).
• Ketone: C=O group (carbonyl group) located in the middle of a chain.

2. Naming Conventions (Nomenclature)

• Alcohol: Replace the alkane suffix “-e” with “-ol” (e.g., ethanol).
• Phenol: Named as phenol, often requiring position numbers.
• Thiol: Use the suffix “-thiol”.
• Ether: Name both alkyl or aryl groups, followed by the word “ether”.
• Aldehyde: Use the suffix “-al”.
• Ketone: Use the suffix “-one”.

Chemical Equilibrium & Enthalpy Changes

Le Chatelier's Principle & Equilibrium Constant (Kc)

• If a reaction is endothermic, an increase in temperature will shift the equilibrium to the right-hand side (products) to decrease the temperature.
• Position of Equilibrium: Describes how far a reaction has proceeded and the proportion of products to reactants in the mixture.
• Equilibrium Constant (Kc): The constant for an equilibrium system, expressed in terms of concentrations (mol dm^-3) at a given temperature.
• Kc Formula: Kc = [Products] / [Reactants]
  • Example (Haber Process): N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
  • Units for Haber Process Kc: (mol dm^-3)^-2 or mol^-2 dm⁶
• Temperature Effects on Kc/Kp:
  • For an exothermic reaction, an increase in temperature decreases Kc/

pure substance: is a phase of uniform composition and unchanging can not be decomposed into other substances of different classes by physical methods.

elements: they are pure substances that can not be decomposed into simpler ones through normal chemical processes.

compounds: they are pure substances made up of two or more elements, which can be decomposed by chemical methods on the elements of which are constituted. A compound always has the same elements and the same proportions regardless of the process followed.

Blended is an aggregation of different substances without causing any chemical reaction between them and therefore may be separated by physical methods.

ponderal laws: they refer to the quantity of matter of different substances... Continue reading "Laws ponderal" »

5. Describe what is electrodeposition, describe the different Experimental methods. Give examples. Advantages and disadvantages. It is the process of production a coating, usually Metallic, on a surface by the action of an electric current._Experimental Methods::-Electroplating: It is a plating process in which metal ions in a Solution are moved by an electric field to coat an electrode. Metallic cations From a solution are reduced on a conductive object (to form a thin layer).-Electrophoretic Deposition:Colloidal particles suspended in a liquid migrate under the Influence of an electric field (electrophoresis) and are deposited onto an Electrode._Advantages: uniform coating thicknen,easy control,high speed of Coating and high pucity._Disadvantages:

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⁺)