Chemical Concepts Explained: Catalysts, Oil, and Molecular Forces

Catalyst

A catalyst is a substance present in a chemical reaction that produces a change in its speed without being consumed during its course. It participates in the reaction but is not altered by it. There are positive catalysts that increase the rate of reaction and negative catalysts that reduce the rate of reaction.

Oil

Oil is a mixture of organic substances—liquid, gaseous, or even solid in solution—mainly abundant in hydrocarbons. Simple hydrocarbons, such as methane, exist, as well as more complex ones that can have up to 40 carbon atoms. Organic compounds with oxygen, such as phenols, are also present. Oil is composed mainly of carbon, a lower percentage of hydrogen, and an even smaller percentage of other elements like nitrogen, oxygen, and sulfur.

Oil is a black substance that undergoes a series of industrial processes in refineries, resulting in many useful applications:

• Motor fuel, including gasoline
• Lubricants
• Asphalt
• Other substances such as paints or plastics

Oil has great economic importance in the development of a country. Regarding its source, the most accepted theory is that it comes from sediments of marine animals and plants (plankton) from ancient times. These sediments underwent different processes in the absence of air under great pressure, giving rise to different hydrocarbons, forming what is known today as crude oil.

Faraday's Law

Faraday's Law has two main statements:

1. The amount of substance deposited or liberated at the electrodes of an electrolytic cell is commensurate with the amount of electricity flowing through it.
2. The total charge required to circulate one mole of electrons through an electrolytic cell is 96,500 C.

Intermolecular Forces

These are forces of attraction between covalent molecules.

Van der Waals Forces (FDE)

These are very weak forces.

Dipole-Dipole Forces

Attractive forces appearing between electric dipoles (polar molecules). The greater the dipole moment, the greater the attractive force (e.g., HCl).

Dipole-Induced Dipole Forces

These occur when a polar molecule induces a temporary dipole in a nearby neutral or non-polarized molecule or atom by displacing its electron cloud. Attraction exists between the dipole (d) and the induced dipole (DI). The strength appears weak (e.g., HF and Ar).

Hydrogen Bonds (Puentes H)

A special electrostatic dipole-dipole interaction that takes place between a hydrogen atom (H) and a small, very electronegative atom (F, O, or N) that forms a highly polarized covalent bond.

Instantaneous Dipole-Induced Dipole Forces

These are forces between non-polarized molecules.

Properties of Metallic Substances

• High melting and boiling points.
• High electrical conductivity in the solid state.
• High thermal conductivity.
• Malleable, ductile, and tenacious.
• Generally insoluble.

Example: Fe (Iron).

Ionic Substances

These are joined by ionic bonding. They are hard, have high boiling points, and are non-conductive (in the solid state). Example: NaCl.