Anyayay's Chemistry Note

The repository contains a structured collection of chemistry notes organized into several key modules:

1. Atomic Structure & Elemental Properties: Electron configuration, Aufbau principle, Pauli exclusion principle, Hund's rule, and periodic laws.
2. Intermolecular Forces & Matter Properties: Crystal structures (molecular, covalent, metallic, ionic) and bonding.
3. Molecular Spatial Structure: VSEPR theory, hybridization, molecular polarity, chirality, and coordination chemistry.
4. Organic Chemistry Fundamentals: Methods of study, structure, nomenclature, hydrocarbons, derivatives, biomolecules, and polymer synthesis.
5. Basic Concepts of Chemical Substances: Stoichiometry, ionic reactions, redox reactions, and chemical common sense.
6. Elements and Their Compounds: Detailed studies of Sodium, Iron, Copper, Magnesium, Aluminum, Halogens, Nitrogen, Sulfur, and Silicon.
7. Chemical Experiments: Laboratory instruments, processes, common experiments, and descriptive templates.
8. Chemical Reaction Energy & Rates: Enthalpy, thermochemical equations, Hess's Law, galvanic cells, electrolytic cells, and reaction kinetics.
9. Chemical Equilibrium: States of chemical equilibrium.

Fats and oils are esters formed from glycerol (propane-1,2,3-triol) and higher fatty acids.

Classification

• Oils: Liquid at room temperature; contain higher proportions of unsaturated fatty acids (containing $\ce{C=C}$ bonds).
• Fats: Solid at room temperature; contain higher proportions of saturated fatty acids.
• Note: Natural oils/fats are usually mixtures of different glycerides and do not have a fixed melting/boiling point.

Chemical Properties

1. Hydrolysis

• Acidic Hydrolysis: Produces higher fatty acids and glycerol.
• Basic Hydrolysis (Saponification): Produces glycerol and higher fatty acid salts (soap). This is used to produce soap via salt-out (salting out) with saturated $\ce{NaCl(aq)}$.

2. Hydrogenation (Hardening)

Unsaturated liquid oils can be converted into semi-solid fats (hardened oils) through catalytic hydrogenation. This increases the saturation level, making the oil more stable against oxidation and easier to store.

Common Fatty Acids

• Saturated:
  • Palmitic acid: $\ce{C15H31COOH}$
  • Stearic acid: $\ce{C17H35COOH}$
• Unsaturated:
  • Oleic acid: $\ce{C17H33COOH}$
  • Linoleic acid: $\ce{C17H31COOH}$

% Saponification (Basic Hydrolysis)
Oil + NaOH ->[\Delta] Glycerol + Fatty Acid Salt (Soap)

% Hydrogenation
Unsaturated Oil + H2 ->[Catalyst] Saturated Fat

Hydride stability and physical properties depend on the position of the element in the periodic table and the type of crystal structure.

Metal Hydride Stability

Stability increases toward the top-left of the periodic table. While elements on the left of a period are more metallic, moving down a group increases atomic radius, which increases bond length and decreases bond energy, lowering stability.

• Example: $\ce{NaH} > \ce{MgH_{2}} > \ce{AlH_{3}}$
• Example: $\ce{LiH} > \ce{NaH} > \ce{KH}$

Non-metal Hydride Stability

Stability increases toward the top-right of the periodic table. Smaller atomic radii in the top-right lead to shorter bond lengths and higher bond energies.

• Example: $\ce{HF} > \ce{HCl} > \ce{HBr} > \ce{HI}$
• Example: $\ce{HF} > \ce{H_{2}O} > \ce{NH_{3}} > \ce{CH_{4}}$

Melting and Boiling Points of Hydrides

• Molecular Crystals: Melting/boiling points are determined by Hydrogen bonding and Van der Waals forces.
  • More hydrogen bonds = higher melting/boiling point.
  • In the absence of hydrogen bonds, a larger relative molecular mass results in a higher melting/boiling point.
• Ionic Crystals: The boiling point of an ionic crystal hydride is always higher than that of a molecular crystal hydride.

Physical Properties

• Colorless, viscous, oily liquid.
• High boiling point and non-volatile.
• Standard concentrated $\ce{H2SO4}$ is $98%$ mass fraction ($18.4\text{ mol/L}$, density $1.84\text{ g/cm}^3$).

Chemical Properties

1. Non-volatility: Used to prepare volatile acids like $\ce{HCl}$ and $\ce{HNO3}$ via heating with salts:
   • $\ce{NaCl + H2SO4(conc) \xlongequal{\Delta} NaHSO4 + HCl \uparrow}$
   • $\ce{NaNO3 + H2SO4(conc) \xlongequal{\Delta} NaHSO4 + HNO3 \uparrow}$
2. Strong Acidity: Used to produce phosphoric acid:
   • $\ce{Ca3(PO4)2 + 3H2SO4(conc) \xlongequal{} 3CaSO4 + 2H3PO4}$
   • Note: $70%$ concentration is often preferred over $98%$ for this reaction to ensure sufficient $\ce{H^+}$ concentration.
3. Dehydrating Property: Can remove hydrogen and oxygen from organic matter in a $2:1$ ratio (e.g., charring sugar or cellulose).
4. Strong Hygroscopicity: Used as a drying agent for gases that do not react with it (e.g., $\ce{O2, H2, N2, CO2, Cl2, HCl, CO, CH4}$).
   • Warning: Cannot be used to dry $\ce{NH3, H2S, HI, HBr}$ due to acid-base or redox reactions.
5. Strong Oxidizing Property: Concentrated $\ce{H2SO4}$ reacts with many substances (e.g., $\ce{Cu, C}$) when heated.
6. Passivation: At room temperature, concentrated $\ce{H2SO4}$ forms a dense oxide film on $\ce{Fe}$ and $\ce{Al}$, protecting them from further reaction. It does not react with $\ce{Cu}$ at room temperature.

In multi-electron atoms, electrons occupy different energy levels within shells.

Energy Shells (能层)

Shells are denoted by symbols $K, L, M, N, O, P, Q...$ corresponding to the principal quantum number $n$ ($n=1, 2, 3...$).

• Energy increases as the shell number $n$ increases.
• Distance from the nucleus increases as the shell number $n$ increases.

Energy Levels (能级)

Within a single shell, electrons are further divided into energy levels based on their orbital type. The order of energy levels within a shell is denoted as $ns, np, nd, nf...$ (where $n$ is the shell number).