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

Heat vs. Enthalpy

Enthalpy is a property of a system, sometimes termed "heat content." It represents the system's internal energy (U) plus the product of pressure and volume (pV).

Heat is energy in transit, transferred between systems. Enthalpy (H) is a state function defining the system's state.

Hess's Law and Enthalpy

Hess's law states that the total enthalpy change for a multi-step reaction equals the sum of enthalpy changes for each individual step. This principle, grounded in the conservation of energy, allows for calculating ΔH even when direct measurement is impossible. It enables the determination of standard enthalpies of formation, useful for designing complex syntheses.

Enthalpy and Reaction Types

Enthalpy determines whether a reaction... Continue reading "Heat vs. Enthalpy, Hess's Law, Reaction Types, and Chemical Properties" »

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Functions of Language

• Expresiva or emotiva: expresses feelings
• Funcion apelativa: incites the receiver
• Representativa: provides information
• Poetica

•Animals, plants, fungi, and most protists depend on mitochondria for energy to grow and survive

•There are more than 100 known mitochondrial disorders (including Luft syndrome)

•Defective mitochondria also contribute to many age-related problems (including Alzheimer’s)

•Aerobic respiration

•Form of cellular respiration in eukaryotes and many prokaryotes

•Oxygen is a reactant in the ATP producing process

•Anaerobic respiration

•Form of cellular respiration in some prokaryotes

•A molecule other than oxygen, such as sulfate or nitrate, is used in the ATP-producing process

•Photosynthesis stores energy from sunlight in electron-rich fuel molecules (such as sugars)

•Cellular respiration moves electrons from fuel to other molecules... Continue reading "Mitochondria, Respiration, and Photosynthesis: Energy Processes in Cells" »

ACID OR BASES: Substances that react with each other according to the following reaction

Nomenclature

Nomenclature: Binary ionic compounds involves combining the names of the compound’s positive and negative ions. The name of the cation is given first, followed by the name of the anion.
Binary compounds: Compounds composed of two elements.

Systems

Stock: uses a Roman numeral to indicate an Ion's charge.

Systematic: naming molecular compounds based on the use of prefixes.

Traditional: the latin names of chemical elements.

Types of Inorganics

Binary Ions: monatomic+monatomic

Ternary Ions: monatomic + polyatomic

Binary Acids: H + monatomic ( Hydro- & -ic acid )

Ternary Oxyacid: H +polyatomic ( -ate, -ide → -ic acid) ( -ite → -ous acid)

Metal oxides

The Mole Concept

The mole concept is an International System unit of measurement for a substance. It is also represented by carbon-12, and 1 mole is equal to Avogadro's number (6.022 x 10^23).

The Periodic Table's Role in Stoichiometric Calculations

We use the periodic table to get values for given elements in a reaction to obtain their atomic values. We can then use these values for conversion from grams to moles or moles to grams in stoichiometric-based problems (gram/mole, mole-gram conversions).

Heat vs. Enthalpy

Heat is the energy that flows between a system and its surroundings due to a difference in temperature.

Enthalpy is equivalent to the total heat content of a system.

Why Only Enthalpy Explains Energy Associated with Chemical Bonds

Because... Continue reading "Principles of Chemistry: From Stoichiometry to Molecular Orbital Theory" »

Fluorine (F): -1

Chlorine (Cl), Bromine (Br), Iodine (I): 1, 3, 5, 7

Sulfur (S), Selenium (Se), Tellurium (Te): 2, 4, 6

Nitrogen: 3, 5

Phosphorus (P), Arsenic (As), Antimony (Sb), Bismuth (Bi): 3, 5

Carbon (C), Silicon (Si): 2, 4

Boron (B): 3

LIthium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), Francium (Fr), Silver (Ag): 1

Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), Radmium (Ra), Zinc (Zn), Cadmium (Cd): 2

Mercury (Hg), Copper (Cu): 1, 2

Tin (Sn), Lead (Pb), Platinum (Pt), Iridium (Ir), Titanium (Ti): 2, 4

Iron (Fe), Cobalt (Co), Nickel (Ni): 2, 3

Gold (Au): 1, 3

Manganese (Mn): 2, 3, (4, 6, 7)

Aluminium (Al): 3

Chromium (Cr): 2, 3, (6)

Chemistry and Physics Basics

Chemistry

The study of the composition, structure, and properties of matter.

Physics

The study of the principles of matter and energy.

Earth Science

The study of Earth and its neighbors in space.

Matter and Its Properties

Mass

A measure of the amount of matter.

Matter

Anything that has mass and takes up space.

Atom

The smallest unit of an element.

Element

A pure substance that cannot be broken down into simpler substances, made up of atoms.

Compound

Made up of elements and can be broken down into simpler substances.

States of Matter

• Liquid: A state of matter that has a definite volume but not a definite shape.
• Gas: A state of matter with no definite volume or shape.
• Plasma: A high-temperature state of matter in which atoms lose most

Ionic Bonds: Electron Transfer

Ionic bonds form when electrons are transferred between atoms, resulting in positively charged cations (+) and negatively charged anions (-).

Covalent Bonds: Electron Sharing

Covalent bonds form when atoms share electrons. This can be visualized by connecting the dots in Lewis structures.

Electronegativity Difference (|ΔEneg|) and Bond Type

• 2.1 - 3.3: Ionic
• 1.7 - 2.0: Borderline (use other information, e.g., boiling/melting points)
• 0.4 - 1.6: Polar Covalent
• 0.0 - 0.3: Non-Polar Covalent

Drawing Covalent Bonds (Lewis Structures)

1. Place the least electronegative element (not Hydrogen) in the center. Count the total number of valence electrons for all atoms.
2. Connect other atoms to the central atom with single bonds (one shared