Notes, summaries, assignments, exams, and exercises for Chemistry for Baccalaureate

Why Life Is Based on Carbon and Not on Silicon

Although silicon (Si) also has four electrons in its valence shell and is much more abundant in the Earth's crust than carbon (C), life is based on C and not on Si. This is because C-C, C=O, and C-N bonds are weak enough to form stable chains and rings, while also being able to break to make way for other molecules. This allows living organisms to obtain the energy contained in these bonds. In contrast, Si-Si and Si-O-Si-O chains are so stable that they are unalterable.

Descriptive Biology

Descriptive biology is based on the simple observation of the structure and functioning of living things, to make descriptions of what is observed. Until the 17th century, it was based solely on simple observation...

Bioelements: Chemical Basis of Life

Bioelements are the chemical elements that constitute living matter. They are classified based on their abundance:

Classification of Bioelements

• Primary Bioelements

  These make up the vast majority of living matter. They include Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), and Sulfur (S) – often abbreviated as CHONPS.

• Secondary Bioelements

  These include Sodium (Na+), Potassium (K+), Calcium (Ca2+), Magnesium (Mg2+), and Chlorine (Cl-). Although present in smaller proportions than primary bioelements, they are essential for life. In aqueous environments within living organisms, they are always found in their ionized forms.

• Trace Elements (Oligoelements)

  These are required in very small amounts.

Chemical Kinetics

Reaction Rate: The change in the concentration of reactants or products per unit time.

For a reaction aA + bB → cC + dD, the rate (v) can be expressed as:

v = -1/a * Δ[A]/Δt = -1/b * Δ[B]/Δt = 1/c * Δ[C]/Δt = 1/d * Δ[D]/Δt

Rate Law: The relationship between the reaction rate and the concentrations of reactants.

v = k [A]^m[B]ⁿ

Where k is the rate constant, and m and n are the reaction orders with respect to A and B, respectively.

Factors Influencing Reaction Rate

• Nature of Reactants: The physical state and chemical properties of reactants affect the rate. Homogeneous reactions (same phase) are often faster than heterogeneous reactions (different phases). In heterogeneous reactions, increasing the surface area increases the

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...

Understanding Physical Sciences

Branches of Physical Science

• Chemistry: The study of the composition, structure, and properties of substances. It is the science that investigates the composition, structure, and properties of matter.
• Physics: The science that deals with matter, energy, motion, and force.
• Earth Science: The study of Earth and its various components.

Why Chemistry is a Physical Science

Chemistry is considered a physical science because it studies what exists around the world, such as atoms and molecules. Physical sciences primarily focus on non-living things.

Fundamental Concepts of Matter

Basic Definitions

• Mass: A measure of the amount of matter in an object.
• Matter: Anything that has mass and takes up space.
• Atom: The smallest unit of

Foundational Atomic Models and Quantum Theory

J.J. Thompson's Atomic Model (1904)

Thompson proposed a particularly simple atomic model based on the discovery of the electron through a series of experiments conducted in low-pressure gas tubes. These experiments confirmed the emission of negatively charged particles, which he called electrons.

Thompson's model (often referred to as the "Plum Pudding Model") considers the atom as a homogeneous sphere of positive charge in which electrons are embedded on its surface, neutralizing the positive charges.

Ernest Rutherford's Nuclear Model (1911)

Rutherford developed his model based on experiments carried out by bombarding thin gold foil with alpha particles. Observations from the experiment included:

• Almost

Nuclear Fusion

Nuclear fusion is a reaction in which two light nuclei combine to form a heavier one. This process releases energy because the weight of the heavier nucleus is less than the sum of the weights of the lighter nuclei. This mass defect is converted to energy, as related by the formula E = mc². Although the mass defect is very small, and the gain per atom is also very small, it must be borne in mind that energy is very concentrated; a small amount of fuel yields a large amount of energy.

Not all fusion reactions produce the same energy; it always depends on the nuclei that bind and the reaction products. The easiest reaction to achieve is the fusion of deuterium (one proton plus one neutron) and tritium (one proton and two neutrons)...

Alkenes: Structure, Reactions, and Synthesis

Hydrogenation of Alkenes

Hydrogenation of alkenes involves the addition of hydrogen across the double bond. This reaction requires a catalyst, such as nickel (Ni) or platinum (Pt), which facilitates the reaction without being consumed. High pressure and temperature conditions are often employed to achieve efficient hydrogenation.

Halogenation of Alkenes

Halogenation of alkenes is an electrophilic addition reaction where a halogen molecule (e.g., Br₂, Cl₂) adds across the double bond. This process often involves the formation of intermediate ions.

During halogenation, the electrophilic halogen attacks the electron-rich double bond, for example, in ethene. This initiates an internal movement of electrons,...

The environment plays an important role in our lives and people wouldn't be able to live without it. However, we are polluting it every day and it needs to stop. As individuals, we can do lots of things to solve this issue, and this essay will focus on two of them - recycling and the efficient use of energy.

According to recycling, it is the easiest way to see an immediate change and everybody can do it. First, recycling bins are a great method of dividing our waste into paper, plastic, glass, etc., and they can be easily found in every city. Another idea is to reuse the things we have at home and make them new. For example, turning …. 

When it comes to the use of energy, there are many things we can do, especially at home. When we talk about...