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Arlon
Online Engineering
Library - TechRef!
Chemistry
Avogadro's Number: The number of elementary particles in a mol of a substance.
1 mol = 1 gram-mole
1 mol = 6.02 x 1023 particles
A mol is defined as an amount of a substance that contains as many particles as 12 grams of 12C (carbon 12). The elementary particles may be atoms, molecules, ions, or electrons.
Acids and Bases (aqueous solutions)
[H+] = molar concentration of hydrogen ion,
Acids have pH < 7
Bases have pH > 7
Electrochemistry
Cathode - The electrode at which reduction occurs.
Anode - The electrode at which oxidation occurs.
Oxidation - The loss of electrons.
Reduction - The gaining of electrons.
Oxidizing Agent - A species that causes others to be oxidized.
Reducing Agent - A species that causes others to be reduced.
Cation - Positive ion
Anion - Negative ion
Definitions
Molarity of Solutions - The number of gram moles of a substance dissolved in a liter of solution.
Molality of Solutions - The number of gram moles of a substance per 1,000 grams of solvent.
Normality of Solutions - The product of the molarity of a solution and the number of valences taking place in a reaction.
Equivalent Mass
- The number of parts by mass of an element or compound which will
combine with or replace directly or indirectly 1.008 parts by mass of
hydrogen, 8.000 parts of oxygen, or the equivalent mass of any other
element or compound. For all elements, the atomic mass is the product
of the equivalent mass and the valence.
Molar Volume of an Ideal Gas [at 0oC (32oF) and 1 atm (14.7 psia)]; 22.4 L/(g mole) [359 ft3/(lb mole)]
Mole Fraction of a Substance
- The ratio of the number of moles of a substance to the total moles
present in a mixture of substances. Mixture may be a solid, a liquid,
or a gas.
Equilibrium Constant of a Chemical Reaction
Le Chatelier's Principle for Chemical Equilibrium
- When a stress (such as a change in concentration, pressure, or
temperature) is applied to a system in equilibrium, the equilibrium
shifts in such a way that tends to relieve the stress.
Heats of Reaction, Solution, Formation, and Combustion
- Chemical processes generally involve the absorption or evolution of
heat. In an endothermic process, heat is absorbed (enthalpy change is
positive). In an exothermic process, heat is evolved (enthalpy change
is negative).
Solubility Product of a slightly soluble substance AB:
AmBn -> mAn+ + nBm-
Solubility Product Constant = KSP = [A+]m [B]n
Metallic Elements
- In general, metallic elements are distinguished from non-metallic
elements by their luster, malleability, conductivity, and usual ability
to form positive ions.
Non-Metallic Elements - In general, non-metallic elements are not malleable, have low electrical conductivity, and rarely form positive ions.
Faraday's Law
- In the process of electrolytic changes, equal quantities of
elecricity charge or discharge equivalent quantities of ions at each
electrode. One gram equivalent weight of matter is chemically altered
at each electrode for 96,485 coulombs, or one Faraday, of electricity
passed through the electrolyte.
A catalyst is a
substance that alters the rate of a chemical reaction and may be
recovered unaltered in nature and amount at the end of the reaction.
The catalyst does not affect the position of equilibrium of a
reversible reaction.
The atomic number is the
number of protons in the atomic nucleus. The atomic number is the
essential feature which distinguishes one element from another and
determines the position of the element in the periodic table.
Boiling Point Elevation
- The presence of a non-volatile solute in a solvent raises the boiling
point of the resulting solution compared to the pure solvent; i.e., to
achieve a given vapor pressure, the temperature of the solution must be
higher than that of the pure substance.
Freezing Point Depression - The presence of a solute lowers the freezing point of the resulting solution compared to that of the pure solvent.
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