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

Chemical Energy and Molecular Bonds

Chemical energy is the energy associated with chemical bonds and intermolecular attraction. The chemical energy of a set of reacting substances changes since bonds break and form new bonds, creating new products.

We call the energy exchanged in the form of heat between a system containing a chemical reaction and its surroundings the heat of reaction.

Exothermic and Endothermic Reactions

• Exothermic Reaction: The energy of the reactants is greater than that of the products and has a negative sign (e.g., combustion). These reactions release chemical energy via heat.
• Endothermic Reaction: The energy in the system grows. The exchange of energy via heat goes from the surroundings toward the system, so the heat of reaction

•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)

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" »

Definition of Average Speed

The average speed of a body is the total distance traveled divided by the total time taken to cover this distance.

Electron Shells in Sodium Ion (Na+)

Na+ is a positively charged sodium ion. Normally, an atom of sodium has 11 electrons; according to the formula, it has 2 electrons in the K shell, 8 electrons in the L shell, and 1 electron in the M shell. However, Na+ has only 10 electrons; therefore, it has 2 electrons in the K shell and 8 in the L shell. Since 2 and 8 are the full capacities of the K and L shells respectively, Na+ has completely filled K and L shells.

Safety Measures in High Jump Events

In a high jump athletic event, athletes are made to fall on either a cushioned bed or a sand bed. If the athlete were... Continue reading "Essential Science Concepts and Physics Calculations" »

Planetary Model of the Atom

An atom has a very small central region, the nucleus, made up of protons and neutrons. The nucleus is surrounded by a cloud of orbiting electrons. The number of electrons in an atom is equal to the number of protons in its nucleus (atoms have no overall electric charge).

Atomic Number (Z)

The atomic number (Z) of an atom is the number of protons it contains. All the atoms of a particular element have the same atomic number. The atoms of different elements have different numbers of protons.

Mass Number (A)

The mass number (A) of an atom is the total number of protons and neutrons it contains. The full chemical symbol for an element shows its mass number at the top and its atomic number at the bottom.

Ions

• Ion: When an atom

Ionic Compounds and Electrical Conductivity

Why ionic compounds do not conduct electricity in the solid state

Explain why ionic compounds do not conduct electricity in their crystalline form. Electricity can only be conducted when ions are moving. In their crystalline form, the ions in the ionic compound are locked tightly in one place.

When ionic compounds are in a solid, crystalline lattice, cations and anions occupy fixed positions in the lattice. Because electric current in ionic materials is carried by mobile charged particles, the fixed ions cannot move and therefore the solid does not conduct electricity. By contrast, when the lattice is melted or dissolved in a polar solvent such as water, ions become free to move and the substance conducts... Continue reading "Why Ionic Compounds Are Nonconductive Solids and Their Properties" »

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

The Pauli Exclusion Principle

The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers. As an orbital can contain a maximum of only two electrons, these two electrons must have opposing spins. This means if one is assigned an up-spin (+1/2), the other must be down-spin (-1/2).

Electrons in the same orbital have the same first three quantum numbers (e.g., n=1, l=0, m_l=0 for the 1s subshell). Only two electrons can have these numbers, so their spin moments must be either m_s = -1/2 or m_s = +1/2. If the 1s orbital contains only one electron, we have one m_s value and the electron configuration is written as 1s¹ (corresponding to hydrogen). If it is fully occupied, we have... Continue reading "Understanding Pauli Exclusion, Hund's Rule, and Aufbau Principle" »